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Miscellaneous Rotating Solitary Waves to a Coupled Dispersionless System
Kuetche Kamgang Victor, Gambo Betchewe, , Bouetou Bouetou Thomas, , Timoleon Crepin Kofane,
Chin. Phys. Lett. 2009, 26 (9):
090505
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DOI: 10.1088/0256-307X/26/9/090505
We investigate the soliton structure of a coupled dispersionless system describing a current-conducting string with infinite length within a magnetic field. Thus, following Hirota's method, we unwrap three typical localized waves with nonzero angular momentum depending strongly upon their angular velocities. Illustrating the soliton behavior of these waves, we focus our interests on breather-like waves and depict the elastic scattering amongst such waves.
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Band Structures of the Nucleus 129Cs
ZHAO Yan-Xin, MA Ying-Jun, ZHOU Wen-Ping, WANG Shou-Yu, LIU Gong-Ye, WU Xiao-Guang, ZHU Li-Hua, HAO Xin, LIU Ying, LI Xue-Qin, LI Ming-Fei
Chin. Phys. Lett. 2009, 26 (9):
092301
.
DOI: 10.1088/0256-307X/26/9/092301
High-spin states in 129Cs are populated via the 122Sn (11B, 4n) reaction at beam energies of 55 and 60MeV. Two additional bands are placed in the level scheme and the previously known bands are extended to higher spins. The results are compared to the cranked shell model calculations and to the systematics of the adjacent Cs isotpoes. One of the new bands is interpreted as the γ-vibrational band built on the π h11/2 orbital. The possible configuration for another new band is discussed. Upbend caused by (ν h11/2)2 alignment is observed both in the favored and unfavored sequences of the π h11/2 configuration. The band based on the π g7/2 configuration at low pins forks around spin 17/2, and the two different S-bands are attributed to (ν h11/2)2 and (π h11/2)2 rotational alignments, respectively.
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Secondary Beam Fragments Produced by 200 and 400MeV/u 12C6+ Ions in Water
ZHAO Qiang, ZHANG Feng-Shou, , WANG Zhi-Ping, ZHOU Hong-Yu,
Chin. Phys. Lett. 2009, 26 (9):
092501
.
DOI: 10.1088/0256-307X/26/9/092501
Based on the GEANT4 toolkit, we study the transportation of nucleons and nuclei in tissue-like media. The fragmentation of projectile nuclei and secondary interactions of produced nuclear fragments are considered. Livermore data is used to calculate electromagnetic interaction of primary and secondary charged particles. We validate the models using experimental data of 200MeV/u and 400MeV/u carbon ions, interacting with tissue equivalent materials of water. The model can well describe the depth-dose distributions in water and the doses measured for secondary fragments of certain charge and certain mass number. The secondary beam fragments produced by 200MeV/u and 400MeV/u 12C6+ ions in water are investigated using the model. When the primary nuclei are in water, several neutron production mechanisms are involved. The light charged particles (p, d, t, 3He and 4He) and fast neutrons contribute to the dose tail behind the Bragg peak. The 11C fragments which may be the most suitable nuclei for monitoring the energy deposition in carbon-ion therapy are also discussed.
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Reinvestigation of Collective Bands in 107Tc
GU Long, ZHU Sheng-Jiang, J. H. Hamilton, A. V. Ramayya, J. K. Hwang, S. H. Liu, WANG Jian-Guo, Y. X. Luo, J. O. Rasmussen, I. Y. Lee, DINGHuai-Bo, K. Li, XU Qiang, YANG Yun-Yi
Chin. Phys. Lett. 2009, 26 (9):
092502
.
DOI: 10.1088/0256-307X/26/9/092502
The high spin states of a neutron-rich 107Tc nucleus are reinvestigated by observing prompt γ-rays from the spontaneous fission of 252Cf. The previous level scheme is updated. A collective band based on the π5/2-[303] orbital is confirmed and extended. Inconsistencies in the configuration assignments for a type of positive parity bands of odd-A 105,107,109Tc in the previous reports are clarified according to the g factor calculations. A new band based on the 1499.5keV level in 107Tc is proposed as a two-phonon γ-vibrational band.
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Development of Mini-LIA and Primary Experiments
CHENG Cheng, LIAO Shu-Qing, ZHENG Shu-Xin, LIN Yu-Zheng, TANG Chuan-Xiang, JING Xiao-Bing, MU Fan, PAN Hai-Feng, ZHANG Kai-Zhi, SHI Jin-Shui, DENG Jian-Jun
Chin. Phys. Lett. 2009, 26 (9):
092902
.
DOI: 10.1088/0256-307X/26/9/092902
Mini-LIA is a miniature of a linear induction accelerator developed by China Academy of Engineering Physics and Tsinghua University in 2007. It has been constructed with a thermionic cathode in an electron injector and a metglas core in the induction accelerator cavities. A double-pulsed electron beam was produced for the first time in China on the Mini-LIA with a thermionic cathode in the electron gun and a metglas core in the induction accelerator cavities. A double-pulsed beam current of more than 1.1A was obtained on condition of 80kV double-pulsed high voltage produced by pulsed power system supplying to the injector and accelerating modules. Some primary experiments for measuring the parameters of Mini-LIA has been performed, and some beam characterizations of Mini-LIA are presented. Further improvement is underway.
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Coherent Control of Photodetachment of H- in Perpendicular Electric and Magnetic Fields
WANG De-Hua, HUANG Kai-Yun
Chin. Phys. Lett. 2009, 26 (9):
093201
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DOI: 10.1088/0256-307X/26/9/093201
Using the semiclassical closed orbit theory, we study the coherent control of the photodetachment of H- by a single and double-pulse laser in perpendicular electric and magnetic fields. Theoretically, dependences of calculated cross section on laser pulse widths, time delays, relative phases and the classical detached electron's closed orbit period are presented and discussed in detail. The results suggest that for the single pulse laser, if the pulse width is shorter than the particular closed orbit period, then the contribution of that closed orbit to the photodetachment cross section is reduced. While for the double pulse laser, the cross section not only depends on the pulse width, but also depends on the time delay and the relative phase of the two pulses. If the pulse delay time equals to the period of one closed orbit, then the contribution of that orbit becomes significant. Therefore, we can use the pulse laser to control the photodetachment process of ion or atom in external fields.
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Cooling and Trapping 88Sr Atoms with 461nm Laser
WANG Shao-Kai, WANG Qiang, LIN Yi-Ge, WANG Min-Ming, LIN Bai-Ke, ZANGEr-Jun, LI Tian-Chu, FANG Zhan-Jun
Chin. Phys. Lett. 2009, 26 (9):
093202
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DOI: 10.1088/0256-307X/26/9/093202
We report the experimental realization of a 88Sr magneto-optical trap (MOT) operating at the wavelength of 461nm. The MOT is loaded via a 32cm long spin-flip type Zeeman slower which enhances the MOT population by a factor of 22. The total laser power available in our experiment is about 300mW. We have trapped 1.6×108 88Sr atoms with a 679nm and 707nm repumping laser. The two repumping lasers enhance the trap population and trap lifetime by factors of 11 and 7, respectively. The 88Sr cloud has a temperature of about 2.3mK, measured by recording the time evolution of the absorption signal.
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Diode-Pumped Quasi-Three-Level Passively Q-Switched Nd:GGG Laser with a Codoped Nd,Cr:YAG Saturable Absorber
HE Kun-Na, GAO Chun-Qing, WEI Zhi-Yi, LI Qi-Nan, ZHANG Zhi-Guo, JIANG Hai-He, YIN Shao-Tang, ZHANG Qing-Li
Chin. Phys. Lett. 2009, 26 (9):
094202
.
DOI: 10.1088/0256-307X/26/9/094202
We demonstrate the first quasi-three-level passively Q-switched Nd:GGG laser at 937nm using a Nd,Cr:YAG crystal as the saturable absorber. The dependences of the average output power, the repetition rate and the pulse width on the incident pump power are obtained. A maximum average output power of 1.18W with repetition rate of 35kHz and pulse width of 45ns is achieved at an incident pump power of 18.3W. The corresponding optical-to-optical and slope efficiencies are 6% and 10%, respectively.
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Tunable Direct Writing of FBGs into a Non-Photosensitive Tm-Doped Fiber Core with an fs Laser and Phase Mask
SONG Cheng-Wei, ZHANG Yun-Jun, WANG Yang, JU You-Lun
Chin. Phys. Lett. 2009, 26 (9):
094204
.
DOI: 10.1088/0256-307X/26/9/094204
Fiber Bragg gratings (FBGs) are successfully written in a non-photosensitive Tm-doped single-mode fiber by a 800nm fs laser and a 2.7μm period phase mask. The intra-core FBGs are written using the phase mask ±1 order interference, and have a period of 1.35μm, which responds to the second-order reflective central wavelength at 1946.4nm. Based on the magnification tuning writing technology, the tunable writing technology is also experimentally investigated. The distance between the phase mask and the fiber, between the phase mask and the tuning lens, and the focal length of the tuning lens all have an influence on the tunable characteristics. Four different FBGs tuning reflective central wavelengths located at 1958.7nm, 1970.8nm, 1882.5nm and 1899.7nm are obtained.
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All-Solid-State Nd:YAG Laser Operating at 1064nm and 1319nm under 885nm Thermally Boosted Pumping
DING Xin, CHEN Na, SHENG Quan, YU Xuan-Yi, XU Xiao-Yan, WEN Wu-Qi, ZHOU Rui, WANG Peng, YAO Jian-Quan,
Chin. Phys. Lett. 2009, 26 (9):
094207
.
DOI: 10.1088/0256-307X/26/9/094207
We report a high-efficiency Nd:YAG laser operating at 1064nm and 1319nm, respectively, thermally boosted pumped by an all-solid-state Q-switched Ti:sapphire laser at 885nm. The maximum outputs of 825.4mW and 459.4mW, at 1064nm and 1319nm respectively, are obtained in a 8-mm-thick 1.1at.% Nd:YAG crystal with 2.1W of incident pump power at 885nm, leading to a high slope efficiency with respect to the absorbed pump power of 68.5% and 42.0%. Comparative results obtained by the traditional pumping at 808nm are presented, showing that the slope efficiency and the threshold with respect to the absorbed pump power at 1064nm under the 885nm pumping are 12.2% higher and 7.3% lower than those of 808nm pumping. At 1319nm, the slope efficiency and the threshold with respect to the absorbed pump power under 885nm pumping are 9.9% higher and 3.5% lower than those of 808nm pumping. The heat generation operating at 1064nm and 1319nm is reduced by 19.8% and 11.1%, respectively.
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Coherence-Time of Matched-Field Processing in Shallow Water in the Presence of Linear Internal Waves
JI Gui-Hua, , LI Zheng-Lin, DAI Qiong-Xing
Chin. Phys. Lett. 2009, 26 (9):
094301
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DOI: 10.1088/0256-307X/26/9/094301
Relationships among the signal coherence-time of matched-field processing (MFP), the acoustic frequency, the source-receiver range, and the sound speed standard deviation (STD) caused by internal waves in shallow water, are numerically investigated based on oceanographic data from two shallow water experiments. It is found that the coherence-time can be fitted with an inverse square-root power of range, a near inverse 1 power of frequency, and inverse 1.3 power of sound speed STD.
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Microstructure and Properties of Cr3Si/γ-Fe Composite Coating Prepared by Plasma Transferred Arc Cladding Technique
LIU Yuan-Fu, CHEN De-Qiang, HAN Jian-Min, WU Hao, XU Xiang-Yang, YANG Si-Ze
Chin. Phys. Lett. 2009, 26 (9):
095202
.
DOI: 10.1088/0256-307X/26/9/095202
Under optimized operating parameters, a wear and corrosion resistant Cr3Si/γ-Fe composite coating is fabricated on a normalized 0.45% carbon steel substrate by using the plasma transferred arc (PTA) cladding technique with Fe-Cr-Si elemental powder blend as the precursor material. Microstructure, microhardness, dry-sliding wear resistance and electrochemical corrosion characteristic of the coating are evaluated. Test results show that the composite coating is mainly composed of primary Cr3Si dendrites and the interdendritic supersaturated iron-base solid solution γ-Fe. Between the Cr3Si/γ-Fe composite coating and the normalized 0.45% carbon steel substrate, there is a narrow metallurgical bonding zone. The Cr3Si/γ-Fe composite coating exhibits high microhardness, excellent wear and corrosion resistance under test conditions.
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Reshock Response of 2A12 Aluminum Alloy at High Pressures
HOU Ri-Li, , PENG Jian-Xiang, JING Fu-Qian, ZHANG Jian-Hua, ZHOU Ping
Chin. Phys. Lett. 2009, 26 (9):
096201
.
DOI: 10.1088/0256-307X/26/9/096201
By means of mounting the specimen on a low-impedance buffer, reshock experiments were carried out on a 2A12 aluminum alloy up to shock stresses of 67.6GPa. Reshock wave profiles from the initial shock stresses of 60.9-67.6GPa were measured with a velocity interferometer, and it shows that the 2A12 aluminum alloy characterizes as quasi-elastic response during recompression process. The Lagrange longitudinal velocities along the reloading path from initial shock state were obtained from two shots of experiments, while the bulk velocities at corresponding shock stresses were determined via extrapolating from the public reported unloading plastic sound velocities. Combining the reshock and the release experimental results, the yield strength of 2A12 aluminum alloy at shock stress of 60.9GPa was estimated to be about 1.7GPa.
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Characterization of Thick GaN Films Directly Grown on Wet-Etching Patterned Sapphire by HVPE
HU Qiang, WEI Tong-Bo, DUAN Rui-Fei, YANG Jian-Kun, HUO Zi-Qiang, LU Tie-Cheng, ZENG Yi-Ping
Chin. Phys. Lett. 2009, 26 (9):
096801
.
DOI: 10.1088/0256-307X/26/9/096801
Thick GaN films of high quality are directly grown on wet-etching patterned sapphire in a vertical hydride vapour phase epitaxy reactor. The optical and structural properties of GaN films are studied using scanning electronic microscopy and cathodoluminescence. Test results show that initial growth of hydride vapour phase epitaxy GaN occurs not only on the mesas but also on the two asymmetric sidewalls of the V-shaped grooves without selectivity. After the two-step coalescence near the interface, the GaN films near the surface keep on growing along the direction perpendicular to the long sidewall. Based on Raman results, GaN of the coalescence region in the grooves has the maximum residual stress and poor crystalline quality over the whole GaN film, and the coalescence process can release the stress. Therefore, stress-free thick GaN films are prepared with smooth and crack-free surfaces by this particular growth mode on wet-etching patterned sapphire substrates.
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Effect of the Pulse Duty Cycle on Characteristics of Plasma Electrolytic Oxidation Coatings Formed on AZ31 Magnesium Alloy
CHEN Huan, LV Guo-Hua, ZHANG Gu-Ling, PANG Hua, WANG Xing-Quan, ZHANG You-Wei, LEE Heon-Ju, YANG Si-Ze,
Chin. Phys. Lett. 2009, 26 (9):
096802
.
DOI: 10.1088/0256-307X/26/9/096802
Ceramic coatings are synthesized on AZ31 magnesium alloy in alkaline silicate solution by the method of plasma electrolytic oxidation. The effect of two different duty cycles (10% and 50%) on the structure and corrosive properties of the coatings is investigated. It is found that the coatings are mainly composed of MgO, Mg2SiO4 and MgF2 through XRD analysis. SEM images indicate that coatings formed at 50% duty cycle have a relatively coarse surface with larger pore size and fewer pores, and have a slower growth rate than those formed at 10% duty cycle with the same treatment time. However, the results of potentiodynamic polarization tests demonstrate that coatings formed at 50% duty cycle exhibit better corrosion resistance as a result of more compact microstructure.
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Conductance in an Aharonov-Bohm Interferometer with Parallel-Coupled Double Dots
AN Xing-Tao, ZHAO Jin-Rong, , LIU Jian-Jun,
Chin. Phys. Lett. 2009, 26 (9):
097201
.
DOI: 10.1088/0256-307X/26/9/097201
We present a theoretical study of the conductance in an Aharonov-Bohm interferometer containing two coupled quantum dots. The interdot tunneling divides the interferometer into two coupled subrings, where opposite magnetic fluxes are threaded separately while the net flux is kept zero. Using the Green function technique we derive the expression of the linear conductance. It is found that the Aharonov-Bohm effect still exists, and when the level of each dot is aligned, the exchange of the Fano and Breit-Wigner resonances in the conductance can be achieved by tuning the magnetic flux. When the two levels are mismatched the exchange may not happen. Further, for some specific asymmetric systems where the coupling strengths between the two dots and the leads are not equal, the flux can change the Fano resonance into an antiresonance, which is absent in symmetric systems.
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Upper Critical Fields and Anisotropy of BaFe1.9Ni0.1As2 Single Crystals
TAO Qian, SHEN Jing-Qin, LI Lin-Jun, LIN Xiao, LUO Yong-Kang, CAO Guang-Han, XU Zhu-An
Chin. Phys. Lett. 2009, 26 (9):
097401
.
DOI: 10.1088/0256-307X/26/9/097401
Temperature dependence of the upper critical magnetic field (Hc2) near Tc of 20K in a BaFe1.9Ni0.1As2 single crystal is determined via magneto-resistance measurements, for the out-plane (H⊥ab) and in-plane (H || ab) directions in magnetic fields of up to 8T. The upper critical fields at zero temperature estimated by the Werthamer-Helfand-Hohenberg (WHH) formula are μ0 Hc2||(0)= 137T and μ0 Hc2⊥(0) = 51T, both exceeding the weak-coupling Pauli paramagnetic limit (μ0Hp=1.84Tc). However, the WHH formula could overestimate the μ0Hc2|| (0) value. The anisotropy of upper critical fields is around 3 in the temperature range close to Tc. The result is very similar to the Co-doped 122 superconductor BaFe2-xCoxAs2, indicating that electron-doped 122 superconductors exhibit similar superconducting properties.
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Mechanism of Pseudogap Detected by Electronic Raman Scattering: Phase Fluctuation or Hidden Order?
LU Hong-Yan, WAN Yuan, HE Xiang-Mei, WANG Qiang-Hua
Chin. Phys. Lett. 2009, 26 (9):
097402
.
DOI: 10.1088/0256-307X/26/9/097402
We study the electronic Raman scattering in the cuprates to distinguish the two possible scenarios of the pseudogap normal state. In one scenario, the pseudogap is assumed to be caused by phase fluctuations of the preformed Cooper pairs. We find that pair-breaking peaks appear in both the B1g and B2g Raman channels, and they are smeared and tend to shift to the same energy with the increasing strength of phase fluctuations. Thus both channels reflect the same pairing energy scale, irrespectively of the doping level. In another scenario, the pseudogap is assumed to be caused by a hidden order that competes with the superconducting order. As an example, we assume that the hidden order is the d-density-wave (DDW) order. We find analytically and numerically that in the DDW normal state there is no Raman peak in the B2g channel in a tight-binding model up to the second nearest-neighbor hopping, while the Raman peak in the B1g channel reflects the energy gap caused by the DDW order. This behavior is in agreement with experiments in the pseudogap normal state. To gain further insights, we also calculate the Raman spectra in the DDW+SC state. We study the doping and temperature dependence of the peak energy in both channels and find a two-gap behavior, which is in agreement with recent Raman experiments. Therefore, our results shed light on the hidden order scenario for the pseudogap.
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Crystal Structure and Magnetic Properties of Sm2Fe17Nδ Thin Films Deposited on Si (100) Substrates
XUE Gang, PENG Long, ZHANG Huai-Wu
Chin. Phys. Lett. 2009, 26 (9):
097503
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DOI: 10.1088/0256-307X/26/9/097503
This work focuses on the crystal structure and magnetic properties of the hard magnetic Sm2Fe17Nδ films prepared by dc magnetron sputtering and the subsequent nitriding process. The XRD, EDS, M-H and M-T data show that N enters the cell structure and the films with the single Th2Zn17 phase are obtained when the nitriding temperature varies from 300 to 400°C, thus the maximum value of the coercivity HC reaches 2561.7Oe. However, the Sm2Fe17 phase decomposes to the SmN nonmagnetic phase and the α-Fe soft magnetic phase with further increasing nitriding temperature, which corresponds to the decreasing HC. Furthermore, the easy magnetization direction (EMD) is found to locate randomly in the film plane. This texture can not give an excellent MR/MS higher than the Stoner-Wohlfarth limitation (MR/MS=0.5), which agrees well with the observed low MR/MS (0.58). It is suggested that the magnetization reversal process is dominated by the nucleation mechanism according to the initial magnetization curve and the dependence of HC on the field H.
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Characteristics of 355nm Laser Damage in KDP and DKDP Crystals
HU Guo-Hang, ZHAO Yuan-An, SUN Shao-Tao, LI Da-Wei, LIU Xiao-Feng, SUN Xun, SHAO Jian-Da, FAN Zheng-Xiu
Chin. Phys. Lett. 2009, 26 (9):
097802
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DOI: 10.1088/0256-307X/26/9/097802
We present the characteristics of bulk damage induced by the third harmonic of Nd:YAG laser irradiation in KDP and DKDP crystals. Bulk damage occurs as a few or a series of pinpoints consisting of a core and the deforming zone. The results of a 1-on-1 test reveal that the pinpoint size increases with incvreasing fluence, and the pinpoint density increases exponentially with increasing fluence. The results of an s-on-1 test indicate that the pinpoint density increases gradually with laser pulse number, but the size does not grow. These results are consistent with a model in which nanoabsorbers are assumed to exist in the crystal and the initiation of damage is determined by heating them to the critical temperature.
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A Thermal Approach to Model Laser Damage in KDP and DKDP Crystals
HU Guo-Hang, ZHAO Yuan-An, SUN Shao-Tao, LI Da-Wei, LIU Xiao-Feng, SUN Xun, SHAO Jian-Da, FAN Zheng-Xiu
Chin. Phys. Lett. 2009, 26 (9):
097803
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DOI: 10.1088/0256-307X/26/9/097803
A thermal model is considered in order to better understand the mechanism of laser induced damage in KDP and DKDP crystals. We demonstrate that the expressions of pinpoint density and damage probability, predicted by the thermal model, are consistent with the experimental data. We also discuss the effect of particle interaction on the thermal model.
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Photoluminescence and X-Ray Photoelectron Spectroscopy of p-Type Phosphorus-Doped ZnO Films Prepared by MOCVD
LI Xiang-Ping, ZHANG Bao-Lin, GUAN He-Song, SHEN Ren-Sheng, PENG Xin-Cun, ZHENG Wei, XIA Xiao-Chuan, ZHAO Wang, DONG Xin, DUGuo-Tong,
Chin. Phys. Lett. 2009, 26 (9):
098101
.
DOI: 10.1088/0256-307X/26/9/098101
Reproducible p-type phosphorus-doped ZnO (p-ZnO:P) films are prepared on semi-insulating InP substrates by metal-organic chemical vapour deposition technology. The electrical properties of these films show a hole concentration of 9.02×1017cm-3, a mobility of 1.05cm2/V s, and a resistivity of 6.6 Ω・cm. Obvious acceptor-bound-exciton-related emission and P-induced zinc vacancy (VZn) emission are observed by low-temperature photoluminescence spectra of the films, and the acceptor binding energy is estimated to be about 125meV. The local chemical bonding environments of the phosphorus atoms in the ZnO are also identified by x-ray photoelectron spectra. Our results show direct experimental evidence that PZn-2VZn shallow acceptor complex most likely contributes to the p-type conductivity of ZnO:P films.
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77 articles
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