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Nanoscale Thermal Response in ZnO Varistors by Atomic Force Microscopy
ZHAO Kun-Yu, ZENG Hua-Rong, LI Guo-Rong, SONG Hong-Zhang, CHENG Li-Hong, HUI Sen-Xing, YIN Qing-Rui
Chin. Phys. Lett. 2009, 26 (10):
100701
.
DOI: 10.1088/0256-307X/26/10/100701
We report the application of customer-built scanning thermal microscopy (SThM) based on a commercial atomic force microscope to investigate local thermal inhomogeneity of ZnO varistors. The so-called 3ω method, generally used for measuring macroscale thermal conductivity, is set up and integrated with an atomic force microscope to probe the nanoscale thermal property. Remarkably, thermal contrasts of ZnO varistors are firstly imaged by the SThM, indicating the uniform distribution of spinel phases at triple points. The frequency-dependent thermal signal of ZnO varistors is also studied to present quantitative evaluation of local thermal conductivity of the sample.
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Measurement of 16O5+ Induced L X-Ray Production Cross Sections for Gold
YANG Zhi-Hu, DU Shu-Bin, CHANG Hong-Wei, XUE Ying-Li, SONG Zhang-Yong, ZHANG Bo-Li, ZHU Ke-Xin, YU De-Yang, CAI Xiao Hong
Chin. Phys. Lett. 2009, 26 (10):
103202
.
DOI: 10.1088/0256-307X/26/10/103202
The characteristic Ll, Lα, Lβ and Lγ x-rays of Au and energy shifts produced by 20-50MeV 16O5+ beams on a thick Au film are measured with a Si (Li)detector. Cross-section ratios of σ(Ll)/σ(Lα), σ(Lβ)/σ(Lα) and σ(Lγ)/σ(Lα) versus O5+ energy show that consistent calculations yield considerably better agreements. Energy shifts Ll, Lα, Lβ and Lγ x-rays of Au target increase with more incidence energy. The main application for these measurements is multi-element trace analysis through particle induced x-ray emission.
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Photodissociation Efficiency Spectroscopy Study of the Rydberg Excited Ion-Pair States of Carbon Dioxide
FENG Qiang, XU Yun-Feng, SUN Jin-Da, TIAN Shan-Xi, SHAN Xiao-Bin, LIU Fu-Yi, SHENG Liu-Si
Chin. Phys. Lett. 2009, 26 (10):
103401
.
DOI: 10.1088/0256-307X/26/10/103401
Photodissociation efficiency spectrum of anionic oxygen atom produced via ion-pair dissociations of carbon dioxide is recorded by means of the synchrotron radiation excitation (XUV photon energy 17.40-20.00eV). The present spectrum is assigned as the Rydberg-like excited ion-pair states, i.e., Tanaka-Ogawa and Henning series, ~C2∑g+ (CO2+) vibrational ground-state and excitation series. Three Rydberg series, npσu, npπu, and nfu, converging to ~C2∑g+ (0,0,0), show the higher cross sections.
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Schemes for Generating Cluster States via Cavity Systems
DU Gang, LAI Bo-Hui, YU Ya-Fei, ZHANG Zhi-Ming
Chin. Phys. Lett. 2009, 26 (10):
104201
.
DOI: 10.1088/0256-307X/26/10/104201
We propose a scheme for generating an N-atom cluster state via cavity quantum electrodynamics (CQED). In our scheme, there is no transfer of quantum information between the atoms and the cavity, i.e., the cavity is always in the vacuum state, so the cavity decay can be suppressed. Also, the generated cluster state is the entanglement of the ground states, so the atomic spontaneous emission can be avoided. Therefore, the cluster state generated in our scheme has a longer lifetime. Furthermore, the requirement on the quality factor of the cavity greatly loosened for the cavity is only virtually excited.
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Measurement of Carrier-Envelope Phase and Field Strength of a Few-Cycle Pulse by Non-sequential Double Ionization
LI Hong-Yun, CHEN Jing, JIANG Hong-Bing, LIU Jie, FU Pan-Ming, GONG Qi-Huang, YAN Zong-Chao, WANG Bing-Bing
Chin. Phys. Lett. 2009, 26 (10):
104207
.
DOI: 10.1088/0256-307X/26/10/104207
We propose a method to measure the carrier-envelop phase (CEP) and the intensity of a few-cycle pulse by controlling the non-sequential double ionization (NSDI) process. By using an additional static electric field, we can change the momentum distribution of the double-charged ions parallel to the laser polarization from an asymmetrical double-hump structure to a nearly symmetrical one. It is found that the ratio between the strength of the static electric field and that of the laser field is sensitive to the CEP but robust against the intensity fluctuation. Therefore we can determine the CEP of a few-cycle pulse precisely by measuring the static electric field. Furthermore, if the CEP of the few-cycle pulse is fixed at a certain value, we can also calibrate the intensity of the laser pulse by the static electric field.
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Beam Ion Transport from Neutron Emissivity Measurement in Deuterium Neutral Beam-Heated Deuterium Plasmas of the HL-2A Tokamak
ISOBE Mitsutaka, LIU Yi, YANG Jin-Wei, CHEN Wei, JI Xiao-Quan, YUAN Guo-Liang, ZHANG Yi-Po, ZOU Gui-Qing, LI Wei, LEI Guang-Jiu, DING Xuan-Tong, YAN Long-Wen, YANG Qing-Wei, DUAN Xu-Ru, OHDACHI Satoshi, MORITA Shigeru, TOI Kazuo
Chin. Phys. Lett. 2009, 26 (10):
105201
.
DOI: 10.1088/0256-307X/26/10/105201
An experiment at the HL-2A tokamak with a high-energy deuterium neutral beam (NB) injection (30keV, about 0.6MW) was performed. The emission of d-d fusion neutrons dominated by beam-plasmas reactions when the deuterium NB was injected into the deuterium target plasma was observed by means of a 235U fission chamber. To obtain information on NB deposition and the slowing down of beam ions in HL-2A plasmas, a very short-pulse deuterium NB injection, or the so-called ``blip'' injection, was performed into MHD-quiescent Ohmic deuterium plasmas. Analysis of neutron decay following the NB ``blip'' injection indicates that tangentially injected beam ions are well confined, slowing down classically in the HL-2A. In contrast to the MHD-quiescent plasma, anomalous losses of beam ions were observed when tearing mode instabilities were present.
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Pressure Effects on Solid State Phase Transformation of Aluminium Bronze in Cooling Process
WANG Hai-Yan, CHEN Yan, LIU Yu-Wen, LI Fei, LIU Jian-Hua, PENG Gui-Rong, WANG Wen-Kui
Chin. Phys. Lett. 2009, 26 (10):
106201
.
DOI: 10.1088/0256-307X/26/10/106201
Effects of high pressure (6GPa) on the solid state phase transformation kinetic parameters of aluminum bronze during the cooling process are investigated, based on the measurement and calculation of its solid state phase transformation temperature, duration and activation energy and the observation of its microstructures. The results show that high pressure treatment can reduce the solid phase transformation temperature and activation energy in the cooling process and can shorten the phase transformation duration, which is favorable when forming fine-grained
aluminum bronze.
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Air Stability of Cs2CO3:Ag/Ag Cathode for Organic Light-Emitting Diodes
LIU Qian, DUAN Lian, ZHANG De-Qiang, QIAO Juan, WANG Li-Duo, QIU Yong
Chin. Phys. Lett. 2009, 26 (10):
106801
.
DOI: 10.1088/0256-307X/26/10/106801
We report the superior stability of the composite Cs2CO3:Ag/Ag cathode structure, which can be used in efficient organic light-emitting diodes (OLEDs). Devices with the Cs2CO3:Ag (1:10, 5nm)/Ag (95nm) cathode show a considerably improved lifetime compared with the control device with the Cs2CO3 (0.5nm)/Ag (100nm) cathode. The composite Cs2CO3:Ag/Ag film is proved to be stable in the atmosphere. X-ray diffraction (XRD) is applied to analyze the crystalline structure of the Cs2CO3:Ag film, and it is demonstrated that CsAg alloy is formed, leading to the improved stability of the thin film and the devices.
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First-Principles Study on the Half-Metallicity of Half-Heusler Alloys: XYZ (X=Mn, Ni; Y=Cr, Mn; Z=As, Sb)
LI Guan-Nan, JIN Ying-Jiu
Chin. Phys. Lett. 2009, 26 (10):
107101
.
DOI: 10.1088/0256-307X/26/10/107101
The electronic structures, magnetism, and half-metallicity of half-Heusler alloys XYZ (X=Mn, Ni; Y=Cr, Mn; Z=As, Sb) are investigated by means of the full-potential linearized augmented plane wave method within the generalized gradient approximation. We consider three types of atomic ordering (i.e., α, β, and γ phases for all of the alloys) and find that the α phase is energetically the most stable. From the calculated density of states and the total magnetic moments, we find that NiMnZ (Z=As, Sb) and NiCrAs are half-metallic ferromagnets, MnCrAs is a half-metallic antiferromagnet, and NiCrSb (MnCrSb) is almost a half-metallic ferromagnet (antiferromagnet).
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Cu Doping Effect on Electrical Resistivity and Seebeck Coefficient of Perovskite-Type LaFeO3 Ceramics
WANG Hong-Chao, WANG Chun-Lei, ZHANG Jia-Liang, ZHAO Ming-Lei, LIU Jian, SU Wen-Bin, YIN Na, MEI Liang-Mo
Chin. Phys. Lett. 2009, 26 (10):
107301
.
DOI: 10.1088/0256-307X/26/10/107301
Perovskite-type LaFe1-xCuxO3 (x=0.10$, 0.14, 0.18) solid solution is prepared with the conventional solid-state reaction technique. The electrical resistivity and the Seebeck coefficient are measured in the temperature range 473-1073K to elucidate the Cu doping effect on the thermoelectric properties of the LaFeO3. The electrical resisitivity of LaFe1-xCuxO3 shows semiconducting behavior. The temperature dependence of the electrical resistivity indicates that the adiabatic small-polaron hopping mechanism is dominant for their electric transportations. The activation energy decreases with the increasing Cu content as well as the increasing temperature. The Seebeck coefficient changes from a negative value to a positive value around 510K, and increases with rising temperature up to 710K, then becomes saturated around 200μV/K. The Seebeck coefficient decreases with the substitution of Cu atoms in the temperature range of 573-1073K, while the electrical resistivity decreases with the substitution of Cu atoms in the whole measured temperature. Overall the power factor increases with rising temperature, and the highest value of power factor is 54μW/K2m for x=0.10 of Cu doping.
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InGaN/GaN p-i-n Photodiodes Fabricated with Mg-Doped p-InGaN Layer
WANG Hui, ZHU Ji-Hong, JIANG De-Sheng, ZHU Jian-Jun, ZHAO De-Gang, LIU Zong-Shun, ZHANG Shu-Ming, YANG Hui,
Chin. Phys. Lett. 2009, 26 (10):
107302
.
DOI: 10.1088/0256-307X/26/10/107302
Mg-doped p-InGaN layers with In composition of about 10% are grown by metalorganic chemical vapor deposition (MOCVD). The effect of the annealing temperature on the p-type behavior of Mg-doped InGaN is studied. It is found that the hole concentration in p-InGaN increases with a rising annealing temperature in the range of 600-850°C, while the hole mobility remains nearly unchanged until the annealing temperature increases up to 750°C, after which it decreases. On the basis of conductive p-type InGaN growth, the p-In0.1Ga0.9N/i-In0.1Ga0.9N/n-GaN junction structure is grown and fabricated into photodiodes. The spectral responsivity of the InGaN/GaN p-i-n photodiodes shows that the peak responsivity at zero bias is in the wavelength range 350-400nm.
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Magnetoresistance in Parent Pnictide AFe2As2(A=Sr, Ba)
ZHENG Ping, CHEN Gen-Fu, LI Zheng, HU Wan-Zheng, DONG Jing, LI Gang, WANG Nan-Lin, LUO Jian-Lin
Chin. Phys. Lett. 2009, 26 (10):
107401
.
DOI: 10.1088/0256-307X/26/10/107401
Magnetoresistances of SrFe2As2 and BaFe2As2 in the magnetic ordered state are studied. Positive magnetoresistance is observed in the magnetic fields H applied in the azimuthes of θta = 0°and 30° with respect to the c-axis. The magnetoresistance can reach 20% for SrFe2As2 and 12% for BaFe2As2 at H = 9 T with θ= 0°(H || c). Above the magnetic transition temperature, the magnetoresistance becomes negligible. The data in the magnetic ordered state could be described by a modified two-band galvanomagnetic model including the enhancement effect of the applied magnetic field on the spin-density-wave gap. The field enhanced spin-density-wave gaps for different types of carriers are different. Temperature dependencies of the fitting parameters are discussed.
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Time-Resolved Photoluminescence of Metamorphic InGaAs Quantum Wells
MA Shan-Shan, WANG Bao-Rui, SUN Bao-Quan, WU Dong-Hai, NI Hai-Qiao, NIU Zhi-Chuan
Chin. Phys. Lett. 2009, 26 (10):
107803
.
DOI: 10.1088/0256-307X/26/10/107803
We investigate the temperature dependence of photoluminescence (PL) and time-resolved PL on the metamorphic InGaAs quantum wells (QWs) with an emission wavelength of 1.55μm at room temperature. Time-resolved PL measurements reveal that the optical properties can be partly improved by introducing antimony (Sb) as a surfactant during the sample growth. The temperature dependence of the radiative lifetime is measured, showing that for QWs grown with Sb assistance, the intrinsic exciton emission is dominated when the temperature is below 60K, while the nonradiative process becomes activated with further increases in temperature. However, without Sb assistance, the nonradiative centers are activated when the temperature is higher than 20K.
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Memory Effect of Metal-Oxide-Silicon Capacitors with Self-Assembly Double-Layer Au Nanocrystals Embedded in Atomic-Layer-Deposited HfO2 Dielectric
HUANG Yue, GOU Hong-Yan, SUN Qing-Qing, DING Shi-Jin, ZHANG Wei, ZHANG Shi-Li,
Chin. Phys. Lett. 2009, 26 (10):
108102
.
DOI: 10.1088/0256-307X/26/10/108102
We report the chemical self-assembly growth of Au nanocrystals on atomic-layer-deposited HfO2 films aminosilanized by (3-Aminopropyl)-trimethoxysilane aforehand for memory applications. The resulting Au nanocrystals show a density of about 4×1011cm-2 and a diameter range of 5-8nm. The metal-oxide-silicon capacitor with double-layer Au nanocrystals embedded in HfO2 dielectric exhibits a large C-V hysteresis window of 11.9V for ± 11V gate voltage sweeps at 1MHz, a flat-band voltage shift of 1.5V after the electrical stress under 7V for 1ms, a leakage current density of 2.9×10-8 A/cm-2 at 9V and room temperature. Compared to single-layer Au nanocrystals, the double-layer Au nanocrystals increase the hysteresis window significantly, and the underlying mechanism is thus discussed.
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67 articles
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