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Volume 31 Issue 5
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Quantum Search Algorithm Based on Multi-Phase
LI Tan, BAO Wan-Su, LIN Wen-Qian, ZHANG Hou, FU Xiang-Qun
Chin. Phys. Lett. 2014, 31 (05): 050301 .   DOI: 10.1088/0256-307X/31/5/050301
Abstract   PDF(pc) (1246KB) ( 653 )

The success probability of the Grover quantum search algorithm decreases quickly when the fraction of target items exceeds 1/4, where the phase plays a significant role. Therefore, we use multiple phases to complement each other. We obtain three useful properties and an important theorem of the success probability and design a systematic solution of the optimal phases for an arbitrary number of phases. Based on these results, we finally propose a multi-phase quantum search algorithm whose success probability rises with the increase of the number of phases with just a single iteration, and it tends to be 100% when the fraction of target items is over a lower limit.

Probing Energy Spectrum of Quadruple Quantum Dots with Microwave Field
SHANG Ru-Nan, LI Hai-Ou, CAO Gang, YU Guo-Dong, XIAO Ming, TU Tao, GUO Guo-Ping
Chin. Phys. Lett. 2014, 31 (05): 050302 .   DOI: 10.1088/0256-307X/31/5/050302
Abstract   PDF(pc) (764KB) ( 515 )
A double quantum dot defines a qubit by a two-level system. The coupling between two qubits induces a double two-level system into a four-level system. We study experimentally the coupling between two capacitive coupled GaAs/AlGaAs double quantum dots while tuning the energy detuning of each double quantum dot simultaneously. Applying microwave photons (at a frequency of 20 GHz) on this system and observing the resonance tunneling with a quantum point contact detector, we obtain an excitation spectrum which is consistent with the numerical simulation result of a coupled two-qubit Hamiltonian. This study demonstrates that a double quantum dot can be exploited as an extraordinary platform for controlled quantum gates.
Arbitrary Partially Entangled Three-Electron W State Concentration with Controlled-Not Gates
SHENG Yu-Bo, FENG Zhao-Feng, OU-YANG Yang, QU Chang-Cheng, ZHOU Lan
Chin. Phys. Lett. 2014, 31 (05): 050303 .   DOI: 10.1088/0256-307X/31/5/050303
Abstract   PDF(pc) (430KB) ( 341 )
We describe an efficient entanglement concentration protocol (ECP) for an arbitrary partially entangled three-electron W state. We show that with the help of two ancillary single electrons, the concentration task can be well completed. This ECP has several advantages: Firstly, we only require one pair of partially entangled states. Secondly, only two single electrons are used during the whole protocol. Thirdly, we do not require all the parties to participate in the whole process, and only two parties are needed to perform the operation. Fourthly, the protocol can be repeated to obtain a high success probability. This ECP may be useful in current quantum computation and quantum communication.
Changes in Repetitive Firing Rate Related to Phase Response Curves for Andronov–Hopf Bifurcations
Yasuomi D. Sato
Chin. Phys. Lett. 2014, 31 (05): 050501 .   DOI: 10.1088/0256-307X/31/5/050501
Abstract   PDF(pc) (515KB) ( 328 )
We study specific changes in repetitive firing in the two-dimensional Hindmarsh–Rose (2dHR) oscillatory system that undergoes a bifurcation transition from the supercritical Andronov–Hopf (AH) type to the subcritical Andronov–Hopf (SAH) type. We identify dynamical mechanisms which are responsible for changes of the repetitive firing rate during the AH to SAH bifurcation transitions. These include frequency-shift functions in response to small perturbations of a timescale parameter, its multiplicative parameter, and an external input current in the 2dHR oscillatory system. The frequency-shift functions are explicitly represented as functions relating to the phase response curves (PRCs). Then, we demonstrate that when the timescale is normal and relatively fast, the repetitive firing rate slightly increases and decreases respectively during the AH to SAH bifurcation transition with a change of the intrinsic parameter, whereas it decreases during the SAH to AH bifurcation transition with an increase in the timescale. By analyzing the three different frequency-shift functions, we show that such changes of the repetitive firing rate depend largely on changes of the PRC size. The PRC size for the SAH bifurcation shrinks to the PRC size for the AH bifurcation.
Effect of Topological Connectivity on Firing Pattern Transitions in Coupled Neurons
LIANG Li-Si, ZHANG Ji-Qian, LIU Le-Zhu, WANG Mao-Sheng, WANG Bing-Hong
Chin. Phys. Lett. 2014, 31 (05): 050502 .   DOI: 10.1088/0256-307X/31/5/050502
Abstract   PDF(pc) (1384KB) ( 279 )
By using the coupled model of Hindmarsh–Rose neuronal systems, we numerically investigate the effect of topology structures on the firing patterns transition (FPT). A four-cell coupled system with all possible configurations are studied. We select the membrane current Iext as a controllable parameter, and set it to be near the left side for one of the bifurcation points. It is found that to have a response from some external stimuli with the proper amplitude and frequencies, the transition will appear between different firing states only when the cells in the system are coupled with some proper topological structures, which implies the occurrence of FPT induced by the configuration in the coupled system. Similar FPT phenomena could also be observed in a five-cell coupled system. Furthermore, we find that such transition behaviors may have some inherent relevance with the synchronization error and the average connective number among cells in the coupled system for different topology structures. These results suggest that the biological neuron systems may achieve an effective response to the external feeble stimulus by selecting the proper configuration and using the corresponding transition mode.
Design of Elliptical Reflection Zone Plate for Monochromatization of the Ultrafast Betatron Radiation at Low Energy Band
YANG Zu-Hua, ZHAO Zong-Qing, WEI Lai, ZHANG Qiang-Qiang, QIAN Feng, GU Yu-Qiu, CAO Lei-Feng
Chin. Phys. Lett. 2014, 31 (05): 050701 .   DOI: 10.1088/0256-307X/31/5/050701
Abstract   PDF(pc) (492KB) ( 257 )
The elliptical reflection zone plate is a kind of optical element in soft x-ray and x-ray ranges and has focusing and dispersion properties. Compared with a transmission zone plate, the required dispersion orders can be easily separated from zeroth order diffraction. It is fabricated on a bulk substrate and does not have much difficulty in the fabrication process. We design a 1000-zone off-axis elliptical reflection zone plate for the monochromatization of the ultrafast betatron radiation at the low energy band, at the designed wavelength of 2.478 nm (500 eV) which is an important spectral part of the betatron radiation, with high spatial resolution, high spectral resolution. Moreover, we simulate the designed reflection zone plate properties. The simulation results show that the spatial resolutions in the spatial direction and the spectral direction are 6.4 μm and 7.3 μm (full width half maximum), respectively, and the spectral resolution reaches up to 496 for the well aligned point source system, which is in good agreement with the theoretical predictions. In addition, we discuss some factors influencing the spectral and spatial resolution, such as the zone number, zone area and the incidence wavelength. The elliptical reflection zone plate also has potential applications in investigating x-ray fluorescence spectra and other fields.
Revisiting 1−+ Light Hybrid from Monte-Carlo Based QCD Sum Rules
ZHANG Zhu-Feng, JIN Hong-Ying, T. G. Steele
Chin. Phys. Lett. 2014, 31 (05): 051201 .   DOI: 10.1088/0256-307X/31/5/051201
Abstract   PDF(pc) (601KB) ( 255 )
We reanalyze the 1?+ light hybrid from QCD sum rules with a Monte-Carlo based on uncertainty analysis. With 30% uncertainties in the accepted central values for QCD condensates and other input parameters, we obtain a prediction on the 1?+ hybrid mass of 1.71 ±0.22 GeV, which covers the mass of π1(1600). We also study the correlations between the input and output parameters of QCD sum rules.
Hadronic Decays of the Spin-Singlet Heavy Quarkomium under the Principle of Maximum Conformality
ZHANG Qiong-Lian, WU Xing-Gang, ZHENG Xu-Chang, WANG Sheng-Quan, FU Hai-Bing, FANG Zhen-Yun
Chin. Phys. Lett. 2014, 31 (05): 051202 .   DOI: 10.1088/0256-307X/31/5/051202
Abstract   PDF(pc) (568KB) ( 185 )

The principle of maximum conformality (PMC) provides a way to eliminate the conventional renormalization scale ambiguity in a systematic way. By applying the PMC scale setting, all non-conformal terms in a perturbative series are summed into the running coupling, and one obtains a unique, scale-fixed prediction at any finite order. In this study, we make a detailed PMC analysis for the spin-singlet heavy quarkoniums decay (into light hadrons) at the next-to-leading order. After applying the PMC scale setting, the decay widths for all those cases are almost independent of the initial renormalization scales. The PMC scales for ηc and hc decays are below 1 GeV; to achieve a confidential pQCD estimation, we adopt several low-energy running coupling models to carry out the estimation. By taking the MPT model, we obtain Γ(ηc →LH)=25.09+5.52−4.28 MeV,Γ(ηb →LH)=14.34+0.92−0.84 MeV, Γ(hc →LH)=0.54+0.06−0.04 MeV and Γ(hb →LH)=39.89+0.28−0.46 keV, where the errors are calculated by taking mc∈[1.40 GeV, 1.60 GeV] and mb∈[4.50 GeV, 4.70 GeV]. These decay widths agree with the principle of minimum sensitivity estimations, in which the decay widths of ηc,b are also consistent with the measured ones.

Doubly Heavy Baryon Production in e+ e Annihilation
YANG Zhong-Juan, ZHANG Pei-Feng, ZHENG Ya-Juan
Chin. Phys. Lett. 2014, 31 (05): 051301 .   DOI: 10.1088/0256-307X/31/5/051301
Abstract   PDF(pc) (486KB) ( 261 )
Considering the inclusive process, we study the doubly heavy baryon Ξcc (Ξbb) production through e+ e? annihilation. Both the diquark QQ in color sextet and triplet are discussed. The results show that the contributions from these two color states play equally important roles. At the Z0 pole, a significant enhancement can be found in the doubly heavy baryon production.
Notch Test for Radial Sensitivity on Neutron Density Distribution in 48Ca Probed by α-Particle Elastic Scattering
ZHANG Xiao-Fu, PANG Dan-Yang
Chin. Phys. Lett. 2014, 31 (05): 052401 .   DOI: 10.1088/0256-307X/31/5/052401
Abstract   PDF(pc) (477KB) ( 187 )
Notch tests are made to study the sensitive regions in the neutron density distribution in the ground state of 48Ca probed by the angular distributions of differential cross sections of α-particle elastic scattering at 104 MeV with optical model potentials calculated by using a systematic single-folding model. An improved notch scheme is proposed, which perturbs the neutron density distribution of the target nucleus locally. Results of the notch tests show that the angular distribution of differential cross sections for α particle elastic scattering at 104 MeV only probe the surface of the neutron density distribution in 48Ca.
Deuterium Retention in the Co-Deposition Carbon Layers Deposited by Radio-Frequency Magnetron Sputtering in D2 Atmosphere
ZHANG Wei-Yuan, SHI Li-Qun, ZHANG Bin, HU Jian-Sheng
Chin. Phys. Lett. 2014, 31 (05): 052901 .   DOI: 10.1088/0256-307X/31/5/052901
Abstract   PDF(pc) (941KB) ( 247 )
Carbon is deposited on C and Si substrates by rf magnetron plasma sputtering in a D2 atmosphere. The deposited layers are examined with ion beam analysis and thermal desorption spectroscopy (TDS). The growth rates of the layers deposited on Si decrease with increasing substrate temperature, while increase significantly with the increase of D2 pressure. Meanwhile, the deuterium concentrations in the layers deposited on the Si substrates decrease from 30% to 2% and from 31% to 1% on the C substrates, respectively, when the substrate temperature varies from 350 K to 900 K. Similarly, the D concentration in the layer on the Si substrates increases from 3.4% to 47%, and from 8% to 35% on the C substrates when the D2 pressure increases from 0.3 Pa to 8.0 Pa. D desorption characterized by TDS is mainly in the forms of D2, HD, HDO, CD4, and C2D4, and a similar release peak occurs at 645 K. The release peak of D2 molecules at 960 K can be attributed to the escaped gas from the thin co-deposited deuterium-rich carbon layer in the form of C–D bonding.
Polarization and Angular Distribution of Lℓ X-Ray Following Inner-Shell 2p3/2 Photoionization of Magnesium-Like Ions
MA Kun, DONG Chen-Zhong, XIE Lu-You, DING Xiao-Bin, QU Yi-Zhi
Chin. Phys. Lett. 2014, 31 (05): 053201 .   DOI: 10.1088/0256-307X/31/5/053201
Abstract   PDF(pc) (714KB) ( 213 )
The inner-shell 2p3/2 photoionization and the subsequent decay of Mg-like Fe14+, Cd36+, W62+ and U80+ ions are studied theoretically within the multiconfiguration Dirac–Fock method and the density matrix theory. Special attention is paid to exploring the influence of the non-dipole terms which arise from the multipole expansion of the electron-photon interaction in the photoionization process. The results show that the non-dipole contribution to the total cross section, the magnetic sublevels cross section of the photoionization process, the degree of linear polarization and angular distribution of the subsequent characteristic x-ray radiation become more important with the increase of photons energy and atomic nuclear Z. Especially for the cross section and the degree of linear polarization, the non-dipole contribution arrives at 50% for U80+ at four time energy threshold units. However, for the angular distribution, the maximum contribution does not exceed 4%, even for U80+ ions.
High-Resolution Selective Excitation of Resonance-Enhanced Multiphoton-Ionization Photoelectron Spectroscopy by Shaping Femtosecond Laser Pulses
CHENG Wen-Jing, ZHANG Shi-An, JIA Tian-Qing, FENG Dong-Hai, SUN Zhen-Rong
Chin. Phys. Lett. 2014, 31 (05): 053301 .   DOI: 10.1088/0256-307X/31/5/053301
Abstract   PDF(pc) (893KB) ( 224 )
Femtosecond laser-induced resonance-enhanced multiphoton-ionization photoelectron spectroscopy (REMPI-PS) is faced with two drawbacks of low spectral resolution and poor selective excitation due to the broad spectral bandwidth. We propose a scheme to obtain a high-resolution selective excitation of (2+1) REMPI-PS by combining π and cosinusoidal phase modulation. Our theoretical results indicate that the (2+1) REMPI-PS signals related to neighboring excited states can be differentiated from their indistinguishable photoelectron spectra by the π phase modulation, and then their selective excitation can be realized by supplementally adding the cosinusoidal phase modulation. Furthermore, the physical mechanism of the high-resolution selective excitation of (2+1) REMPI-PS is explained by considering the two-photon power spectrum.
Multi-Band Absorption Properties and Near-Field Enhancement in Mid-Infrared Based on the Interference Theory
Chin. Phys. Lett. 2014, 31 (05): 054201 .   DOI: 10.1088/0256-307X/31/5/054201
Abstract   PDF(pc) (952KB) ( 214 )
We numerically study the multi-band absorption properties and near-field enhancement inside the microcavity based on the interference theory. The compact single unit cell consists of a gold square patch placed on the top of a metallic ground plane, separated by a dielectric layer. At the normal incidence of electromagnetic radiation, four bands of a maximum absorption of 98% are accomplished by appropriate sizes of the square patch. Furthermore, we demonstrate that the four bands, which are corresponding to the fundamental mode and higher modes of the standing wave, can be readily tuned in the mid-infrared region and associated with the near-field enhancement in the cuboid microcavity. Since chemical and biological fingerprints of the common functional groups can be found in the mid-infrared region, we may readily tune the multi-bands of interest in the mid-infrared range and identify the molecular stretches of groups. Moreover, the proposed structure is insensitive to the polarization of the incident wave due to the complete rotational symmetry (C4 symmetry). The unique properties of the optical metamaterial indicate that this approach is a promising strategy for surface-enhanced infrared absorption spectroscopy and for the tracking of characteristic molecular vibrational modes
Brillouin Lasing with a Reduced Self-Pulsing Characteristic Using a Short-Length Erbium-Doped Fiber as the Nonlinear Gain Medium
A. Zarei, R. Z. R. R. Rosdin, N. M. Ali, H. Ahmad, S. W. Harun
Chin. Phys. Lett. 2014, 31 (05): 054202 .   DOI: 10.1088/0256-307X/31/5/054202
Abstract   PDF(pc) (678KB) ( 252 )
A single-wavelength Brillouin laser is demonstrated by using a 3-m-long erbium doped fiber (EDF) in a ring cavity. The EDF is used to provide both nonlinear and linear gains to generate a stimulated Brillouin scattering (SBS) and to amplify the generated SBS, respectively. The Brillouin erbium fiber laser (BEFL) operates at 1561.5 nm, where the operating wavelength is up-shifted by 0.08 nm from the Brillouin pump. The operation wavelength is also tunable within 1560.6–1562.6 nm. The BEFL also shows a self-pulsing characteristic with repetition of 66.7 kHz when the BP is set around the threshold pump power of 13 mW. Compared to the conventional Brillouin fiber laser with a long cavity length, the proposed BEFL exhibits a significantly lower amplitude of pulse. This laser has many potential applications, such as in optical communication and sensors.
Measurement of Diffusion Coefficient of Liquids by Using an Asymmetric Liquid-Core Cylindrical Lens: Observing the Diffusion Process Directly
LI Qiang, PU Xiao-Yun, YANG Rui-Fen, ZHAI Ying
Chin. Phys. Lett. 2014, 31 (05): 054203 .   DOI: 10.1088/0256-307X/31/5/054203
Abstract   PDF(pc) (533KB) ( 360 )
We report a method for measuring diffusion coefficient D of liquids by using an aplanatic and asymmetric cylinder lens with a liquid core, which is designed as both a diffusion pool and the main imaging element. The precision is better than 10?4 RIU in measuring refractive index. The D values of ethylene glycol (EG) in water are measured for various EG concentrations at 25°C, and Dinf=1.043×10?5 cm2/s under the condition of infinite dilution is obtained. The method is characterized by observing the diffusion process directly, faster measurement and obtaining the D value under the condition of infinite dilution.
Room-Temperature Operation of 2.4 µm InGaAsSb/AlGaAsSb Quantum-Well Laser Diodes with Low-Threshold Current Density
XING Jun-Liang, ZHANG Yu, LIAO Yong-Ping, WANG Juan, XIANG Wei, XU Ying-Qiang, WANG Guo-Wei, REN Zheng-Wei, NIU Zhi-Chuan
Chin. Phys. Lett. 2014, 31 (05): 054204 .   DOI: 10.1088/0256-307X/31/5/054204
Abstract   PDF(pc) (643KB) ( 296 )
GaSb-based 2.4 μm InGaAsSb/AlGaAsSb type-I quantum-well laser diode is fabricated. The laser is designed consisting of three In0.35Ga0.65As0.1Sb0.9/Al0.35Ga0.65As0.02Sb0.98 quantum wells with 1% compressive strain located in the central part of an undoped Al0.35Ga0.65As0.02Sb0.98 waveguide layer. The output power of the laser with a 50-μm-wide 1-mm-long cavity is 28 mW, and the threshold current density is 400 A/cm2 under continuous wave operation mode at room temperature.
Multiband Metamaterial Absorber at Terahertz Frequencies
XU Zong-Cheng, GAO Run-Mei, DING Chun-Feng, ZHANG Ya-Ting, YAO Jian-Quan
Chin. Phys. Lett. 2014, 31 (05): 054205 .   DOI: 10.1088/0256-307X/31/5/054205
Abstract   PDF(pc) (529KB) ( 441 )
We propose a multi-band metamaterial absorber operating at terahertz frequencies. The design, characterization, and theoretical calculation of the high performance metamaterial absorber are reported. The multi-band metamaterial absorber consists of two metallic layers separated by a dielectric spacer. Theoretical and simulated results show that the metamaterial absorber has four distinct absorption points at frequencies 0.57 THz, 1.03 THz, 1.44 THz and 1.89 THz, with the absorption rates of 99.9%, 90.3%, 83.0%, 96.1%, respectively. Two single band metamaterial absorbers and a dual band metamaterial absorber on the top layer are designed. Some multi-band absorbers can be designed by virtue of combining some single band absorbers. The multiple-reflection theory is used to explain the absorption mechanism of our investigated structures.
Visible Light Driven Photocatalytic Reactor Based on Micro-structured Polymer Optical Fiber Preform
LI Dong-Dong, SHE Jiang-Bo, WANG Chang-Shun, PENG Bo
Chin. Phys. Lett. 2014, 31 (05): 054206 .   DOI: 10.1088/0256-307X/31/5/054206
Abstract   PDF(pc) (644KB) ( 180 )
A novel visible light driven photocatalytic reactor with 547 pieces of Ag/AgBr-film-modified capillaries is reported and it is derived from a microstructured polymer optical fiber (MPOF) preform. The MPOF preform not only plays the role of a light-transmitting media, but it is also a Ag/AgBr supporting and waste-water pipe to supply the photocatalytic degradation of dyes solute. The photocatalytic reactor has such a large surface area for Ag/AgBr loading, which is a visible light driven photocatalyst that photodegradation efficiency is enhanced.
Suppression of the Resonant Scattering in Imperfect Acoustic Cloaking with a Lossy Medium in 3
LI Meng-Lei, KIM Seungil
Chin. Phys. Lett. 2014, 31 (05): 054301 .   DOI: 10.1088/0256-307X/31/5/054301
Abstract   PDF(pc) (551KB) ( 246 )
It has been realized that resonance frequencies of imperfect acoustic cloaking based on a small perturbation of the transformation acoustics in ?2 are located near Dirichlet eigenvalues of the cloaked region [Chin. Phys. Lett. 26 (2009) 014301; 29 (2012) 124301]. In this work, we study the performance of the three-dimensional approximate cloaking system based on the transformation acoustics and show that the cloaking effect may be deteriorated at zeroth order Neumann eigenvalues of the concealed region. In particular, transmitted fields into the concealed region can be extremely resonated at frequencies corresponding to the zeroth-order Neumann eigenvalues while scattered fields are suppressed well for any frequency. To enhance the cloaking effect at resonance frequencies, we introduce a lossy medium inside the cloaked region and show that the new proposal can reduce the intensity of transmitted fields significantly due to the lossy medium.
Novel Image Optimization Method for Joint Photoacoustic Tomography
LI Wen-Chao, YUAN Jie, SHEN Qing-Hong, YU Yao, ZHOU Yu, DU Si-Dan, LIU Xiao-Jun, XU Guan, WANG Xue-Ding
Chin. Phys. Lett. 2014, 31 (05): 054302 .   DOI: 10.1088/0256-307X/31/5/054302
Abstract   PDF(pc) (953KB) ( 213 )
The distribution of speed of sound (SOS) in biomedical tissue and delay compensation (DC) have significant impact on the image quality of photoacoustic tomography (PAT). When imaging human peripheral joints, using fixed SOS and DC can only ensure that the reconstructed images are focused in a limited depth range, whereas they are defocused at other depths, which cause severe artifacts and blurring. In this work, a linear-DC based reconstruction approach is proposed to focus the whole PAT image region. It is proved by two in vivo experiments that, compared with traditional delay-and-sum back projection algorithms, the proposed method can effectively optimize the image quality of articular tissues in PAT.
Fast Electron Spatial Temperature Distribution Studied by X-Ray 2D Imaging
TIAN Ye, WANG Wen-Tao, XIA Chang-Quan, WANG Cheng, XU Yi, LI Wen-Tao, QI Rong, ZHANG Zhi-Jun, LIANG Hong, YU Chang-Hai, LENG Yu-Xin, LIU Jian-Sheng
Chin. Phys. Lett. 2014, 31 (05): 055201 .   DOI: 10.1088/0256-307X/31/5/055201
Abstract   PDF(pc) (747KB) ( 293 )
We present the experimental and numerical results of two-dimensional x-ray imaging due to fast electron transport in a solid target. A 40-μm-thick copper film target is irradiated by a 100 mJ, 50 fs normal incident laser pulse. The full width at half maximum of the x-ray photon dose is 25 μm, and the divergence angle of fast electrons is 25°–30°, which is detected by the pin-hole x-ray imaging technique. The target surface plasma layer is compressed by a ponderomotive force into a depth of 0.2λ. The plasma wave accompanied by fast electrons transporting into the target is studied by dividing the plasma into layers in a radial direction. A narrow fast electron channel, which is approximately 8 μm–10 μm in width, mainly contributes to the x-ray dose.
Spectroscopic Diagnostics of Atmospheric Argon Microwave Plasma Based on an Inductive Coupling Window-Rectangular Resonator
WANG Zhong, ZHANG Gui-Xin, LIU Cheng, JIA Zhi-Dong
Chin. Phys. Lett. 2014, 31 (05): 055202 .   DOI: 10.1088/0256-307X/31/5/055202
Abstract   PDF(pc) (834KB) ( 303 )
We present a novel microwave plasma source based on an inductive coupling window-rectangular resonator. A definite volume of atmospheric argon microwave plasma is excited in the source under the input of several kilowatts of microwave power operating at 2.45 GHz. The excitation temperature and electron temperature of the argon plasma are separately researched by using Boltzmann plot and line-to continuum intensity ratio of Ar I spectral lines. Its electron density is inferred from the Stark broadening of the Hβ line at 486.13 nm.
Comparative Study on Excitation Temperature, Electron Temperature and Electron Density in an Atmospheric Argon Microwave Plasma
WANG Zhong, ZHANG Gui-Xin, LIU Cheng, JIA Zhi-Dong
Chin. Phys. Lett. 2014, 31 (05): 055203 .   DOI: 10.1088/0256-307X/31/5/055203
Abstract   PDF(pc) (880KB) ( 283 )
An infinite-volume of atmospheric argon microwave plasma is produced in the microwave plasma source based on the inductive coupling window-rectangular resonator under the input of the microwave power at 2.45 GHz. The excitation temperature of the plasma is studied by using the Boltzmann plot of Ar I lines in two different wavelength ranges while the electron temperature is researched by using line-to-continuum intensity ratio of Ar I lines. The electron density is compared by using the Stark broadenings of Ar I lines at 522.13 nm and 549.59 nm and Hβ line at 486.13 nm.
Synthesis and Photoluminescence Properties of GaAs Nanowires Grown on Fused Quartz Substrates
ZHAO Yu-Feng, LI Xin-Hua, SHI Tong-Fei, WANG Wen-Bo, ZHOU Bu-Kang, DUAN Hua-Hua, ZENG Xue-Song, LI Ning, WANG Yu-Qi
Chin. Phys. Lett. 2014, 31 (05): 056101 .   DOI: 10.1088/0256-307X/31/5/056101
Abstract   PDF(pc) (645KB) ( 281 )
GaAs nanowires are synthesized on fused quartz substrates by using molecular beam epitaxy via a vapor-liquid-solid mechanism with gold as the catalyst. High resolution-transmission electron microscopy is used to probe crystal quality and growth direction. Micro-photoluminescence measurements are carried out to examine the optical properties of GaAs NWs. The low-temperature photoluminescence (PL) emission of nanowires (NWs) has a peak at 1.513 eV, 2 meV lower than the zinc blende GaAs free exciton energy. The temperature-dependent band gap of NWs is seen to be somewhat different from that observed in bulk GaAs, and the PL rapidly quenches above 150 K, with an activation energy of 6.3 meV reflecting the presence of the longitudinal twins' structure.
The Near Surface Morphology of P3HT:PCBM Blend Films Studied by Near-Edge X-Ray Absorption Fine Structure
ZENG Xue-Song, SHI Tong-Fei, YE Chang-Hui, LI Ning, LI Xin-Hua, WANG Yu-Qi
Chin. Phys. Lett. 2014, 31 (05): 056102 .   DOI: 10.1088/0256-307X/31/5/056102
Abstract   PDF(pc) (700KB) ( 287 )
The microstructure of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) blends with various annealing temperatures are investigated in detail by the near-edge x-ray absorption fine structure. Under higher annealing temperature (Tanneal160°C), P3HT shows an unusual fluidity and aggregation in the surface. After annealing, the enrichment polymer component recrystallizes and forms a single P3HT phase layer in the surface of blend films. Moreover, it gives direct evidence of the PCBM content diffusing to the near surface of blend films during annealing treatment. These findings are beneficial to improving the morphology of polymer/fullerene blend films.
Quasi-hydrostatic Limit of LiF as a Pressure Transmitting Medium and Its Equation of States
GUO Jia-Zeng, WU Ye, ZHU Feng, WU Xiang, YANG Ke, QIN Shan
Chin. Phys. Lett. 2014, 31 (05): 056201 .   DOI: 10.1088/0256-307X/31/5/056201
Abstract   PDF(pc) (523KB) ( 212 )
Quasihydrostatic limit of LiF as a pressure transmitting medium is investigated by synchrotron radiation x-ray diffraction combined with the diamond anvil cells technique up to 60 GPa at room temperature. The equation-of-state parameters of LiF are determined to be V0=65.7(2) ?3, B0=58(3) GPa and B0'=4.9(2) in the silicon oil environment; V0=67.4(3) ?3, B0=51(3) GPa and B0'=4.7(2) without pressure transmitting medium. The full width at half maximum of LiF (111) peak increases with the increase of pressure in two independent experiments. The pressure distribution in the sample chamber is estimated by line-scanning x-ray diffraction measurements across the chamber's center, which presents as homogeneous with Pmax?Pmin of about 1 GPa below 40 GPa.
Effect of Stress in GaN/AlInGaN Grown on GaN Templates with Different Stress States
FENG Xiang-Xu, LIU Nai-Xin, ZHANG Ning, WEI Tong-Bo, WANG Jun-Xi, LI Jin-Min
Chin. Phys. Lett. 2014, 31 (05): 056801 .   DOI: 10.1088/0256-307X/31/5/056801
Abstract   PDF(pc) (671KB) ( 216 )
We clarify the effect of the stress in GaN templates on the subsequent AlInGaN deposition by simply growing 150 nm AlInGaN on a 30 μm GaN template (sample 1) prepared by hydride vapor phase epitaxy and a 2.3 μm thin control GaN template (sample 2) prepared by metalorganic chemical vapor deposition. X-ray diffraction and secondary iron mass spectroscopy measurements reveal the stress states (tensile stress and full relaxed for samples 1 and 2, respectively) and compositions (Al0.169In0.01 Ga0.821N, Al0.171In0.006Ga0.823N for samples 1 and 2, respectively) of AlInGaN. By carefully eliminating other possible factor, as template surface roughness, it is concluded that different stress states of AlInGaN should stem from different stress states of GaN templates.
Synthesis and Growth Mechanism: A Novel Fishing Rod-Shaped GaN Nanorods
ZHANG Shi-Ying, XIU Xiang-Qian, HUA Xue-Mei, XIE Zi-Li, LIU Bin, CHEN Peng, HAN Ping, LU Hai, ZHANG Rong, ZHENG You-Dou
Chin. Phys. Lett. 2014, 31 (05): 056802 .   DOI: 10.1088/0256-307X/31/5/056802
Abstract   PDF(pc) (804KB) ( 315 )
A novel fishing rod-shaped GaN nanorod is successfully fabricated through a new method by using the two-step growth technology. This growth method is applicable to continuous synthesis and is able to produce a large number of single-crystalline GaN nanorods with a relatively high purity and at a low cost. X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy are used to characterize the as-synthesized nanorods. The results show that most of the nanorods consist of a main rod and a top curved thread. It is single-crystal GaN with hexagonal wurtzite structure. The representative photoluminescence spectrum at room temperature exhibits a strong UV light emission band centered at 370.8 nm. Furthermore, a possible two-stage growth mechanism of the fishing rod-shaped GaN nanorod is also briefly discussed.
A Wafer-Level Sn-Rich Au–Sn Bonding Technique and Its Application in Surface Plasmon Resonance Sensors
MAO Xu, LV Xing-Dong, WEI Wei-Wei, ZHANG Zhe, YANG Jin-Ling, QI Zhi-Mei, YANG Fu-Hua
Chin. Phys. Lett. 2014, 31 (05): 056803 .   DOI: 10.1088/0256-307X/31/5/056803
Abstract   PDF(pc) (754KB) ( 238 )
Sn-rich Au–Sn solder bonding is systematically investigated. High shear strength (64 MPa) and good hermeticity (a leak rate lower than 1×10?7 torr?l/s) are obtained for Au–Sn solder with 54 wt% Sn bonded at 310°C. The AuSn2 phase with the highest Vickers-hardness among the four stable intermetallic compounds of the Au–Sn system makes a major contribution to the high bonding strength. This bonding technique has been successfully used to package the Surface Plasmon Resonance (SPR) sensors. The Sn-rich Au–Sn solder bonding provides a reliable, low-cost, low-temperature and wafer-level hermetic packaging solution for the micro-electromechanical system devices and has potential applications in high-end biomedical sensors.
Stabilization of η-Cu6Sn5 Intermetallic Compound by Zn Addition: First-Principles Investigation
ZHOU Wei, LIU Yan-Yu
Chin. Phys. Lett. 2014, 31 (05): 057101 .   DOI: 10.1088/0256-307X/31/5/057101
Abstract   PDF(pc) (1504KB) ( 1247 )
The structural phase transformation and electronic properties of Cu6Sn5 with and without Zn addition are analyzed based on the first principles calculations. The results indicate that the energy difference between the η phase and the η' phase decreases significantly after Zn addition at finite temperature. This implies that the high temperature η-phase Cu6(Sn,Zn)5 will be stabilized. Moreover, the bulk modulus is also improved after Zn addition. We attribute the corresponding structural stabilization to the relatively strong Zn–Cu and Zn–Sn bonding in the η-Cu6(Sn,Zn)5.
A Numerical Method for Modeling the Effects of Irregular Shape on Interconnect Resistance
CHEN Bao-Jun, TANG Zhen-An, JU Yan-Jie
Chin. Phys. Lett. 2014, 31 (05): 057102 .   DOI: 10.1088/0256-307X/31/5/057102
Abstract   PDF(pc) (502KB) ( 195 )
When clock frequencies exceed gigahertz, the skin depth in analog and digital circuits greatly decreases. The irregular shape of the cross section of the interconnect plays an increasingly important role in interconnect parasitic extraction. However, existing methods only focus on the rough surface of the interconnect, while ignoring other irregular shapes, such as the trapezoidal cross section. In this work, a new simulation method is proposed for irregular interconnects, which is applicable to arbitrary irregular shapes and to a wide range of frequencies. The method involves generating a mesh information file firstly, and then extracting the frequency-dependent resistance based on a numerical solution of scalar wave modeling by using the method of moments. The singularity extraction method is used to calculate the self-inductors. The data from experiments verify the accuracy of our proposed method.
Fano Resonance by Symmetry Breaking Stub in a Metal-Dielectric-Metal Waveguide
TANG Dong-Hua, DING Wei-Qiang
Chin. Phys. Lett. 2014, 31 (05): 057301 .   DOI: 10.1088/0256-307X/31/5/057301
Abstract   PDF(pc) (518KB) ( 298 )
The coupling of a stub obliquely intersected with a metal-dielectric-metal plasmonic waveguide is investigated by using the finite difference in time domain method. Results show that an odd mode, except for the usual even mode, is excited in the stub due to the symmetry breaking of the oblique intersection. Moreover, the results show that the quality factor of the odd mode is very high in comparison with that of the usual even mode, which is then explained by the symmetry breaking of the oblique stub intersection. The superposition of the even and the odd mode generates a Fano shaped spectrum with a very narrow linewidth. The effect of metallic loss and compensation are also discussed. Both the stub and the waveguide are compact in size, and simple in structure, which are beneficial for the achievements of narrow band filtering, sensing, lasing, and nonlinearity enhancement.
Rectification Effect of the Heat Generation by Electric Current in a Quantum Dot Molecular
LI Bo-Xin, ZHENG Jun, CHI Feng
Chin. Phys. Lett. 2014, 31 (05): 057302 .   DOI: 10.1088/0256-307X/31/5/057302
Abstract   PDF(pc) (673KB) ( 219 )
We study the heat generation by an electric current in a quantum dot (QD) molecular coupled to a single-model phonon bath in the Coulomb blockade regime. It is found that when the system is driven out of equilibrium by the thermal bias applied across the two terminals of the structure, the heat flowing between the QD and the phonon bath can be very small for one direction of the thermal bias, while it becomes quite large when the corresponding direction of the thermal bias is reversed. The device thus operates as a heat rectifier or heat diode. Moreover, the heat generation can be suppressed to negative values by the thermal bias. We emphasize that the above-mentioned two effects are beyond the reach of the usual electric bias.
Forward Current Transport Mechanisms of Ni/Au–InAlN/AlN/GaN Schottky Diodes
WANG Xiao-Feng, SHAO Zhen-Guang, CHEN Dun-Jun, LU Hai, ZHANG Rong, ZHENG You-Dou
Chin. Phys. Lett. 2014, 31 (05): 057303 .   DOI: 10.1088/0256-307X/31/5/057303
Abstract   PDF(pc) (712KB) ( 216 )
We fabricate two Ni/Au-In0.17Al0.83N/AlN/GaN Schottky diodes on substrates of sapphire and Si, respectively, and investigate their forward-bias current transport mechanisms by temperature-dependent current-voltage measurements. In the temperature range of 300–485 K, the Schottky barrier heights (SBHs) calculated by using the conventional thermionic-emission (TE) model are strongly positively dependent on temperature, which is in contrast to the negative-temperature-dependent characteristic of traditional semiconductor Schottky diodes. By fitting the forward-bias IV characteristics using different current transport models, we find that the tunneling current model can describe generally the IV behaviors in the entire measured range of temperature. Under the high forward bias, the traditional TE mechanism also gives a good fit to the measured IV data, and the actual barrier heights calculated according to the fitting TE curve are 1.434 and 1.413 eV at 300 K for InAlN/AlN/GaN Schottky diodes on Si and the sapphire substrate, respectively, and the barrier height shows a slightly negative temperature coefficient. In addition, a formula is given to estimate SBHs of Ni/Au–InAlN/AlN/GaN Schottky diodes taking the Fermi-level pinning effect into account.
Electronic Transport of a Molecular Photoswitch with Graphene Nanoribbon Electrodes
WU Qiu-Hua, ZHAO Peng, LIU De-Sheng
Chin. Phys. Lett. 2014, 31 (05): 057304 .   DOI: 10.1088/0256-307X/31/5/057304
Abstract   PDF(pc) (938KB) ( 311 )
Based on non-equilibrium Green's function formalism and density functional theory calculations, we investigate the electronic transport properties of 15,16-dinitrile dihydropyrene/cyclophanediene bridged between two zigzag graphene nanoribbon electrodes. Our results demonstrate that the system can exhibit good switching behavior with the maximum on-off ratio high up to 146 which is improved dramatically compared with the case of gold electrodes. Moreover, an obvious negative differential resistance behavior occurs at 0.3 V, making the system have more potential in near future molecular circuits.
Electroforming-Free and Highly Uniform Al2O3 Resistive Random Access Memory by ALD-Based In Situ Hydrogen Plasma Treatment
WU Hua-Yu, ZHANG Jian, ZHANG Qi-Long, YANG Hui, LUO Ji-Kui
Chin. Phys. Lett. 2014, 31 (05): 057305 .   DOI: 10.1088/0256-307X/31/5/057305
Abstract   PDF(pc) (790KB) ( 288 )
Al2O3 resistive random access memory (RRAM) with electroforming-free characteristics, high stability and uniform properties is fabricated. The effect of the in situ hydrogen plasma enhanced treatment on the device performance is investigated. The dominated conduction mechanisms of the devices are ohmic behavior at low fields and space charge limited charge injection at high fields. The great improvement in the device properties is attributed to the hydrogen plasma treatment with the Al2O3 film, and this simple while effective atomic layer deposition based plasma treatment process is expected to be useful for other RRAM material systems as well.
Manipulation of Surface Plasmon Polaritons by Phase Modulation of Source Field with Inverse Problem Algorithm
LIU Chun-Xiang, LIANG Guo-Tao, ZHANG Mei-Na, LI Zhen-Hua, CHENG Chuan-Fu
Chin. Phys. Lett. 2014, 31 (05): 057306 .   DOI: 10.1088/0256-307X/31/5/057306
Abstract   PDF(pc) (885KB) ( 220 )
The predetermined field distributions can be achieved by phase modulation of the source field to manipulate the propagation of surface plasmon polaritons (SPPs). The modulations of the radius of the circular slit are according to the phase distributions on the slit, which are calculated by using the Gerchberg–Saxton algorithm with the known field. We design the surface geometric shape of the radius-varied circular slit for exciting the SPP field with the linear, triangular, square and circular distribution characteristics, respectively. The slit structure designed for the circular field distribution is a plasmonic vortex lens that can be used to generate the vortex with the specified size of the primary ring, which shows that this heuristic method has the potential to devise plasmonic devices.
Role of Oxygen Vacancy Arrangement on the Formation of a Conductive Filament in a ZnO Thin Film
ZHAO Jing, DONG Jing-Yu, ZHAO Xu, CHEN Wei
Chin. Phys. Lett. 2014, 31 (05): 057307 .   DOI: 10.1088/0256-307X/31/5/057307
Abstract   PDF(pc) (710KB) ( 226 )
We perform first-principles calculations for ZnO thin films with oxygen vacancy defects. The densities of states, partial atomic densities of states, charge density differences and atomic populations are presented. We show that the SET process, i.e., from a high resistive state to a low resistive state, is attributable to the aggregation and regular arrangement of the oxygen vacancies, which causes the formation of conductive filaments and leads to the low resistive state of the system.
An Exotic Type of Fulde–Ferrel–Larkin–Ovchinnikov States in Spin-Orbit Coupled Condensates
HAN Qiang, LIU Jia, ZHANG Dan-Bo, WANG Zi-Dan
Chin. Phys. Lett. 2014, 31 (05): 057401 .   DOI: 10.1088/0256-307X/31/5/057401
Abstract   PDF(pc) (596KB) ( 224 )
We find for the first time that a model Hamiltonian of s-wave superconductors in the presence of spin-orbit interactions and a Zeeman field is exactly solvable. Most intriguingly, based on the exact solutions, a novel type of Fulde–Ferrel–Larkin–Ovchinnikov ground state is rigorously revealed, in which the center-of-mass momentum of the fermion pair is proportional to the Zeeman field. We also generalize our exact analysis to the spin-orbit-coupled Bose–Einstein condensate.
Effective Field Based on the Exchange Interaction in Gd3Ga5O12 under Low and Moderate Magnetic Field at Low Temperature
HU Feng, ZHANG Guo-Ying, HUANG Yi-Jia, XIA Wang-Suo
Chin. Phys. Lett. 2014, 31 (05): 057501 .   DOI: 10.1088/0256-307X/31/5/057501
Abstract   PDF(pc) (649KB) ( 196 )
The roles of the exchange interaction between different magnetic ions in the gadolinium gallium garnet Gd3Ga5O12 are systematically investigated. The effective field based on the exchange interaction is expressed as functions of the temperature T and applied field He. Furthermore, the effects of T and He on the magnetic moment and the entropy of Gd3Ga5O12 are studied in the ranges of 0<He<9 T and 3<T<40 K. The computational results are consistent with the experimental data. Our study reveals that the applied field and temperature have important influences on the exchange interaction of Gd3Ga5O12 at low temperature.
Temperature Dependence of Luminescence of CdS:Mn/ZnS Core-Shell Quantum Dots
FANG Dai-Feng, WANG Zhong-Ping, DAI Ru-Cheng, ZHANG Zeng-Ming, DING Ze-Jun
Chin. Phys. Lett. 2014, 31 (05): 057801 .   DOI: 10.1088/0256-307X/31/5/057801
Abstract   PDF(pc) (907KB) ( 278 )
Luminescence intensity of CdS:Mn/ZnS core-shell quantum dots (QDs) can be strongly enhanced in comparison with bulk CdS:Mn and nanoparticles, while the luminescence due to the surface state is greatly suppressed by a capping ZnS shell. We find that with the increasing temperature, the peak position of CdS:Mn/ZnS core-shell QDs blue shifts due to the reduction of phonon coupling. Unlike the bulk CdS:Mn, the luminescence of the core-shell QDs is less sensitive to thermal quenching.
Determination of the In-Plane Optical Conductivity of Multilayer Graphene Supported on a Transparent Substrate of Finite Thickness from Normal-Incidence Transmission Spectra
Chin. Phys. Lett. 2014, 31 (05): 057802 .   DOI: 10.1088/0256-307X/31/5/057802
Abstract   PDF(pc) (536KB) ( 267 )
Normal-incidence transmission measurements are commonly used for determining the real part of the in-plane optical conductivities σ1(ω) of graphene layers. We present an accurate expression for σ1(ω) in a closed form for a multilayer graphene film supported on a finite-thickness transparent substrate. This form takes into account the coherent and incoherent multiple reflections of the system, whereas the traditional method assumes a semi-infinite substrate. The simulated results for graphene sheets with a layer number N≤10 show that no matter what the transparent substrate is, the accuracy to which σ1(ω) is determined by applying this expression is improved with no systematic error. Moreover, the layer number N can be exactly determined by simply dividing the σ1(ωp) value of N-layer graphene by the corresponding σ1(ωp) of monolayer graphene, where ωp is the peak frequency of the ordinary dielectric function's imaginary part ε2(ω) of graphene.
Electrically Pumped Ultraviolet Random Lasing from p-ZnO:As Based on p-ZnO/N-GaN Heterojunction
ZHANG Yuan-Tao, XIA Xiao-Chuan, WU Bin, SHI Zhi-Feng, YANG Fan, YANG Xiao-Tian, ZHANG Bao-Lin, DU Guo-Tong
Chin. Phys. Lett. 2014, 31 (05): 058101 .   DOI: 10.1088/0256-307X/31/5/058101
Abstract   PDF(pc) (606KB) ( 196 )
p-ZnO:As is prepared by the GaAs interlayer doping method. The potential applications of p-ZnO:As are evaluated by applying it into the construction of a p-ZnO/n-GaN heterojunction, though its hall, electrochemical capacitance-voltage and photoluminescence results show a hole concentration at the level of ~1017 cm?3 and a good optical quality. Ultraviolet random lasing is detected from the studied device under forward bias. Specific lasing modes are confirmed to originate from p-ZnO:As by further introducing the p-ZnO/MgO/n-GaN heterostructure. The resulting random lasing phenomena demonstrate the promising prospects in device application of p-ZnO:As fabricated by using our methods.
Improved Performance of Phthalocyanine Derivative Field-Effect Transistors by Inserting a Para-Quarterphenyl as the Inducing Layer
DONG Ni, WU Xiao-Ming, DANG Huan-Qin, LIU Dong-Yue, ZHANG Qiang, WEI Jun, YIN Shou-Gen
Chin. Phys. Lett. 2014, 31 (05): 058501 .   DOI: 10.1088/0256-307X/31/5/058501
Abstract   PDF(pc) (1019KB) ( 264 )
We investigate the phthalocyanine derivative organic field-effect transistors (OFETs) using a novel para -quaterphenyl (p-4p) as the inducing layer. Compared to the devices without the p-4p inducing layer, the performances of p-type (copper phthalocyanine) and n-type (fluorinated copper phthalocyanine) OFETs with optimized thickness of p-4p thin films are greatly enhanced. Both the field-effect mobility and the on/off ratio of the two-type devices are improved by one order of magnitude compared to those of the control devices. This remarkable improvement is attributed to the introduction of p-4p, which can form a highly oriented and continuous phthalocyanine derivative film with the molecular ππ stack direction parallel to the substrate.
A Silicon-Based Positive-Intrinsic-Negative Photodetector Double Linear Array on a Thick Intrinsic Epitaxial Layer
YUAN Li, WU Can, ZHANG Zhao-Hua, REN Tian-Ling
Chin. Phys. Lett. 2014, 31 (05): 058502 .   DOI: 10.1088/0256-307X/31/5/058502
Abstract   PDF(pc) (1555KB) ( 222 )
To measure small particles in clouds without the optical amplification system, a new type of p-i-n photodetector linear array with 128 diode units altogether is designed and realized. In each die, there are two rows of photodiode line array, and each row has 64 photodiodes. Every photodiode has a size of 100 μm × 100 μm with an individual output, and each of them is isolated by the trenches. The depth of them has the same thickness as that of the epitaxial layer, which is designed to be 30 μm to guarantee sufficient absorption of photons and leave a margin for the diffusion of p-type and n-type region. The detector has been tested with a laser whose wavelength was 650 nm and irradiance is 50 mW/cm2. The achieved photocurrent is 2 μA. Hence, the current responsivity is about 0.4 A/W, and the external quantum efficiency is 76.45%. The dark current is less than 600 pA. Both of the sufficient absorption of photons and low dark current are achieved by utilizing the thick epitaxial intrinsic layer. Low interference of adjacent photodiodes is also guaranteed by the trenches around the photodiodes. With the obtained performance, the photodetector can be used to measure the diameter of precipitation particles in clouds. Therefore, rainfall can be judged based on the diameter of particles.
Germanium PMOSFETs with Low-Temperature Si2H6 Passivation Featuring High Hole Mobility and Superior Negative Bias Temperature Instability
WANG Hong-Juan, HAN Gen-Quan, LIU Yan, YAN Jing, ZHANG Chun-Fu, ZHANG Jin-Cheng, HAO Yue
Chin. Phys. Lett. 2014, 31 (05): 058503 .   DOI: 10.1088/0256-307X/31/5/058503
Abstract   PDF(pc) (772KB) ( 206 )
We investigate negative bias temperature instability (NBTI) on high performance Ge p?channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) with low-temperature Si2H6 passivation. The Ge pMOSFETs exhibit an effective hole mobility of 311 cm2/V?s at an inversion charge density of 2.5×1012 cm?2. NBTI characterization is performed to investigate the linear transconductance (GM, lin) degradation and threshold voltage shift (ΔVTH) under NBT stress. Ge pMOSFETs with a 10 yr lifetime at an operating voltage of -0.72 V are demonstrated. The impact of the Si2H6 passivation temperature is studied. As the passivation temperature increases from 350°C to 550°C, the degradation of NBTI characteristics, e.g., GM, lin loss, ΔVTH and an operating voltage for a lifetime of 10 yr, is observed.
Nanoscale Phase Separation-Induced Suppression of Geminate Recombination in Low Bandgap Polymer-Fullerene Solar Cells
LIU Jian, WU Jiang, SHAO Shu-Yan, XIE Zhi-Yuan, GUO Shi-Jie
Chin. Phys. Lett. 2014, 31 (05): 058801 .   DOI: 10.1088/0256-307X/31/5/058801
Abstract   PDF(pc) (1638KB) ( 317 )
The short-circuit current of polymer solar cells based on a PCPDTBT:PC71BM blend is substantially increased by using a processing additive. It is found that the significant geminate recombination in the PCPDTBT:PC71BM blend film is dramatically suppressed by using a processing additive which can produce a nanoscale PCPDTBT and PC71BM phase separation. The processing additive-induced aggregation of PCPDTBT polymer chains and PC71BM molecules can give rise to a driving force for the separation of charge-transfer states at the donor/acceptor interfaces into the free charge carriers and thus geminate recombination is suppressed.
48 articles