| Record 1 of 15 |
| Author(s): Kang, J (Kang, Jun); Zhang, Y (Zhang, Yang); Wen, YH (Wen, Yu-Hua); Zheng, JC (Zheng, Jin-Cheng); Zhu, ZZ (Zhu, Zi-Zhong) |
| Title: First-principles study on the structural and electronic properties of ultrathin ZnO nanofilms |
| Source: PHYSICS LETTERS A, 374 (8): 1054-1058 FEB 8 2010 |
| Abstract: Using first-principles density-functional calculations, we have studied the structural and electronic properties Of Ultrathin ZnO {0001} nanofilms. The structural parameters, the charge densities, band structures and density of states have been investigated. The results show that there are remarkable charge transfers from Zn to O atoms in the ZOO nanofilms. All the ZOO nanofilms exhibit direct wide band gaps compared with bulk counterpart, and the gap decreases with increased thickness of the nanofilms. The decreased band gap is associated with the weaker ionic bonding within layers and the less localization of electrons in thicker films. A staircase-like density of states occurs at the bottom of conduction band, indicating the two-dimensional quantum effects in ZnO nanofilms. (C) 2009 Elsevier B.V. All rights reserved. |
| ISSN: 0375-9601 |
| DOI: 10.1016/j.physleta.2009.12.031 |
| Record 2 of 15 |
| Author(s): Ding, F (Ding, F.); Singh, R (Singh, R.); Plumhof, JD (Plumhof, J. D.); Zander, T (Zander, T.); Krapek, V (Krapek, V.); Chen, YH (Chen, Y. H.); Benyoucef, M (Benyoucef, M.); Zwiller, V (Zwiller, V.); Dorr, K (Doerr, K.); Bester, G (Bester, G.); Rastelli, A (Rastelli, A.); Schmidt, OG (Schmidt, O. G.) |
| Title: Tuning the Exciton Binding Energies in Single Self-Assembled InGaAs/GaAs Quantum Dots by Piezoelectric-Induced Biaxial Stress |
| Source: PHYSICAL REVIEW LETTERS, 104 (6): Art. No. 067405 FEB 12 2010 |
| Abstract: We study the effect of an external biaxial stress on the light emission of single InGaAs/GaAs(001) quantum dots placed onto piezoelectric actuators. With increasing compression, the emission blueshifts and the binding energies of the positive trion (X+) and biexciton (XX) relative to the neutral exciton (X) show a monotonic increase. This phenomenon is mainly ascribed to changes in electron and hole localization and it provides a robust method to achieve color coincidence in the emission of X and XX, which is a prerequisite for the possible generation of entangled photon pairs via the recently proposed "time reordering'' scheme. |
| ISSN: 0031-9007 |
| Article Number: 067405 |
| DOI: 10.1103/PhysRevLett.104.067405 |
| Record 3 of 15 |
| Author(s): Shi, HL (Shi, Hongliang); Zhang, P (Zhang, Ping); Li, SS (Li, Shu-Shen); Wang, BT (Wang, Baotian); Sun, B (Sun, Bo) |
| Title: First-principles study of UC2 and U2C3 |
| Source: JOURNAL OF NUCLEAR MATERIALS, 396 (2-3): 218-222 JAN 31 2010 |
| Abstract: The electronic structure and mechanical properties Of UC2 and U2C3 have been systematically investigated using first-principles calculations by the projector-augmented-wave (PAW) method. Furthermore, in order to describe precisely the strong on-site Coulomb repulsion among the localized U 5f electrons, we adopt the generalized gradient approximation +U formalisms for the exchange-correlation term. We show that our calculated structural parameters and electronic properties for UC2 and U2C3 are in good agreement with the experimental data by choosing an appropriate Hubbard U = 3 eV. As for the chemical bonding nature, the contour plot of charge density and total density of states suggest that UC2 and U2C3 are metallic mainly contributed by the 5f electrons, mixed with significant covalent component resulted from the strong C-C bonds. The present results also illustrate that the metal-carbon (U-C) bonding and the carbon-carbon covalent bonding in U2C3 are somewhat weaker than those in UC2, leading to the weaker thermodynamic stability at high temperature as observed by experiments. (C) 2009 Elsevier B.V. All rights reserved. |
| ISSN: 0022-3115 |
| DOI: 10.1016/j.jnucmat.2009.11.009 |
| Record 4 of 15 |
| Author(s): Wen, Q (Wen, Qian); Zhang, RF (Zhang, Rufan); Qian, WZ (Qian, Weizhong); Wang, YR (Wang, Yuran); Tan, PH (Tan, Pingheng); Nie, JQ (Nie, Jingqi); Wei, F (Wei, Fei) |
| Title: Growing 20 cm Long DWNTs/TWNTs at a Rapid Growth Rate of 80-90 mu m/s |
| Source: CHEMISTRY OF MATERIALS, 22 (4): 1294-1296 FEB 23 2010 |
| ISSN: 0897-4756 |
| DOI: 10.1021/cm903866z |
| Record 5 of 15 |
| Author(s): Yan, J (Yan, Jun); Sun, CH (Sun, Chenghua); Tan, FR (Tan, Furui); Hu, XJ (Hu, Xiujie); Chen, P (Chen, Ping); Qu, SC (Qu, Shengchun); Zhou, SY (Zhou, Shuyun); Xu, JK (Xu, Jingkun) |
| Title: Electropolymerized poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) film on ITO glass and its application in photovoltaic device |
| Source: SOLAR ENERGY MATERIALS AND SOLAR CELLS, 94 (2): 390-394 FEB 2010 |
| Abstract: Poly(3,4-ethylenedioxythiopliene):poly(styrene sulfonate) (PEDOT:PSS) films have been electrochemically polymerized in situ on ITO glass substrate in boron trifluoride diethyl etherate electrolyte (BFEE). Cyclic voltammograms show good redox activity and stability of the PEDOT films. These films had been directly used to fabricate organic-inorganic hybrid solar cells with the structure of ITO/PEDOT/ZnO:MDMC-PPV/Al. The solar cells made of electrochemically polymerized films exhibit higher energy conversion efficiencies compared with that prepared by the spin-coating method, and the highest value is 0.33%. This in-situ electropolymerized method effectively simplifies fabricating procedures and may blaze a facile and economical route for producing high-efficiency solar cells. (C) 2009 Elsevier B.V. All rights reserved. |
| ISSN: 0927-0248 |
| DOI: 10.1016/j.solmat.2009.09.014 |
| Record 6 of 15 |
| Author(s): Zhao, L (Zhao, L.); Zuo, YH (Zuo, Y. H.); Zhou, CL (Zhou, C. L.); Li, HL (Li, H. L.); Diao, HW (Diao, H. W.); Wang, WJ (Wang, W. J.) |
| Title: A highly efficient light-trapping structure for thin-film silicon solar cells |
| Source: SOLAR ENERGY, 84 (1): 110-115 JAN 2010 |
| Abstract: A highly efficient light-trapping structure, consisting of a diffractive grating, a distributed Bragg reflector (DBR) and a metal reflector was proposed. As an example, the proposed light-trapping structure with an indium tin oxide (ITO) diffraction grating, an a-Si:H/ITO DBR and an Ag reflector was optimized by the simulation via rigorous coupled-wave analysis (RCWA) for a 2.0-mu m-thick c-Si solar cell with an optimized ITO front antireflection (AR) layer under the air mass 1.5 (AM1.5) solar illumination. The weighted absorptance under the AM1.5 solar spectrum (A(AM1.5)) of the solar cell can reach to 69%, if the DBR is composed of 4 pairs of a-Si:H/ITOs. If the number of a-Si:H/ITO pairs is up to 8, a larger A(AM1.5) of 72% can be obtained. In contrast, if the Ag reflector is not adopted, the combination of the optimized ITO diffraction grating and the 8-pair a-Si:H/ITO DBR can only result in an A(AM1.5) of 68%. As the reference, A(AM1.5) = 31% for the solar cell only with the optimized ITO front AR layer. So, the proposed structure can make the sunlight highly trapped in the solar cell. The adoption of the metal reflector is helpful to obtain highly efficient light-trapping effect with less number of DBR pairs, which makes that such light-trapping structure can be fabricated easily. (C) 2009 Elsevier Ltd. All rights reserved. |
| ISSN: 0038-092X |
| DOI: 10.1016/j.solener.2009.10.014 |
| Record 7 of 15 |
| Author(s): Xu, XS (Xu, Xingsheng); Yamada, T (Yamada, Toshiki); Yokoyama, S (Yokoyama, Shiyoshi) |
| Title: Modification of two-photon excited fluorescence from quantum dots on SiN photonic crystals |
| Source: OPTICS LETTERS, 35 (3): 309-311 FEB 1 2010 |
| Abstract: We investigate two-photon excited fluorescence from CdSe quantum dots with a center-emitting wavelength of 655 nm on SiN photonic crystals. We find that two-photon excited fluorescence is enhanced by more than 1 order of magnitude in the vertical direction when a photonic crystal is used compared to the fluorescence spectra in the absence of photonic crystals. The spectrum of two-photon excited fluorescence from quantum dots on SiN photonic crystal is observed to shift to blue compared to that from quantum dots on SiN without photonic crystals. (C) 2010 Optical Society of America |
| ISSN: 0146-9592 |
| Record 8 of 15 |
| Author(s): Jia, CH (Jia, C. H.); Chen, YH (Chen, Y. H.); Zhou, XL (Zhou, X. L.); Liu, GH (Liu, G. H.); Guo, Y (Guo, Y.); Liu, XL (Liu, X. L.); Yang, SY (Yang, S. Y.); Wang, ZG (Wang, Z. G.) |
| Title: InN layers grown by MOCVD on SrTiO3 substrates |
| Source: JOURNAL OF CRYSTAL GROWTH, 312 (3): 373-377 JAN 15 2010 |
| Abstract: Epitaxial wurtzite InN thin films have been grown by metal-organic chemical vapor deposition on (1 1 1) SrTiO3 (STO) substrates. Interestingly, twin domain epitaxy induced by the surface reconstruction of STO is observed with the in-plane orientation relationships of [(1) over bar 1 0 0]InN parallel to [<(1)over bar > 1 0]STO and [2 <(1 1)over bar > 0]InN parallel to[<(1)over bar > 1 0]STO, which is helpful to release the strain. The InN films on STO substrates exhibit a strong photoluminescence emission around 0.78 eV. Particularly, using STO substrates opens up a possibility to integrate InN with the functional oxides. (C) 2009 Elsevier B.V. All rights reserved |
| ISSN: 0022-0248 |
| DOI: 10.1016/j.jcrysgro.2009.10.066 |
| Record 9 of 15 |
| Author(s): Zhu, NH (Zhu, Ning Hua); Man, JW (Man, Jiang Wei); Zhang, HG (Zhang, Hong Guang); Ke, JH (Ke, Jian Hong); Han, W (Han, Wei); Chen, W (Chen, Wei); Liu, Y (Liu, Yu); Wang, X (Wang, Xin); Yuan, HQ (Yuan, Hai Qing); Xie, L (Xie, Liang) |
| Title: Lineshape Analysis of the Beat Signal Between Optical Carrier and Delayed Sidebands |
| Source: IEEE JOURNAL OF QUANTUM ELECTRONICS, 46 (3): 347-353 MAR 2010 |
| Abstract: This paper presents the lineshape analysis of the beat signal between the optical carrier and the shifted and delayed side-bands produced by sinusoidal amplitude modulation. It is shown that the beat signal has a typical lineshape with a very narrow delta-peak superposed on a quasi-Lorentzian profile. Theoretical explanation for the appearance of this peak has been given based on optical spectral structure constructed by a large number of optical wave trains. It is predicted that the delta-peak is originated from the beat between the wave trains in the carrier and those in the delayed sidebands when their average coherence length is longer than the delay line. Experiments carried out using different delay lines clearly show that the delta-peak is always located at the modulation frequency and decreases with the increasing delay line. Our analysis explicitly indicates that the linewidth is related to the observation time. It is also suggested that the disappearance of the delta-peak can be used as the criterion of coherence elimination. |
| ISSN: 0018-9197 |
| DOI: 10.1109/JQE.2009.2033214 |
| Record 10 of 15 |
| Author(s): Xie, YY (Xie Yi-Yang); Xu, C (Xu Chen); Kan, Q (Kan Qiang); Wang, CX (Wang Chun-Xia); Liu, YM (Liu Ying-Ming); Wang, BQ (Wang Bao-Qiang); Cheng, HD (Cheng Hong-Da); Shen, GD (Shen Guang-Di) |
| Title: A Single-Fundamental-Mode Photonic Crystal Vertical Cavity Surface Emitting Laser |
| Source: CHINESE PHYSICS LETTERS, 27 (2): Art. No. 024206 FEB 2010 |
| Abstract: Single-fundamental-mode photonic crystal (PhC) vertical cavity surface emitting lasers (VCSEL) are produced and their single-fundamental-mode performances are investigated and demonstrated. A two-dimensional PhC with single-point-defect structure is fabricated using UV photolithography and inductive coupled plasma reactive ion etching on the surface of the VCSEL's top distributed Bragg-reflector. The PhC VCSEL maintains single-fundamental-mode operating with output power 1.7 mW and threshold current 2.5 mA. The full width half maximum of the lasing spectrum is less than 0.1 nm, the far field divergence angle is less than 10 degrees and the side mode suppression ratio is over 35 dB. The device characteristics are analyzed based on the effective index model of the photonic crystal fiber. The experimental results agree well with the theoretical expectation. |
| ISSN: 0256-307X |
| Article Number: 024206 |
| DOI: 10.1088/0256-307X/27/2/024206 |
| Record 11 of 15 |
| Author(s): Xing, MX (Xing Ming-Xin); Zheng, WH (Zheng Wan-Hua); Zhou, WJ (Zhou Wen-Jun); Chen, W (Chen Wei); Liu, AJ (Liu An-Jin); Wang, HL (Wang Hai-Ling) |
| Title: Slow Light Effect and Multimode Lasing in a Photonic Crystal Waveguide Microlaser |
| Source: CHINESE PHYSICS LETTERS, 27 (2): Art. No. 024213 FEB 2010 |
| Abstract: The slow light effect in a photonic crystal waveguide is investigated theoretically and experimentally. Theoretical calculation indicates that there is a slow light region for the even mode, from which the resonance and lasing in a microcavity would benefit. A photonic crystal waveguide microlaser is fabricated, which is related to the group velocity of c/120.6. |
| ISSN: 0256-307X |
| Article Number: 024213 |
| DOI: 10.1088/0256-307X/27/2/024213 |
| Record 12 of 15 |
| Author(s): Ji, HM (Ji Hai-Ming); Yang, T (Yang Tao); Cao, YL (Cao Yu-Lian); Xu, PF (Xu Peng-Fei); Gu, YX (Gu Yong-Xian); Ma, WQ (Ma Wen-Quan); Wang, ZG (Wang Zhan-Guo) |
| Title: High Characteristic Temperature 1.3 mu m InAs/GaAs Quantum-Dot Lasers Grown by Molecular Beam Epitaxy |
| Source: CHINESE PHYSICS LETTERS, 27 (2): Art. No. 027801 FEB 2010 |
| Abstract: We report the molecular beam epitaxy growth of 1.3 mu m InAs/GaAs quantum-dot (QD) lasers with high characteristic temperature T-0. The active region of the lasers consists of five-layer InAs QDs with p-type modulation doping. Devices with a stripe width of 4 mu m and a cavity length of 1200 mu m are fabricated and tested in the pulsed regime under different temperatures. It is found that T-0 of the QD lasers is as high as 532K in the temperature range from 10 degrees C to 60 degrees C. In addition, the aging test for the lasers under continuous wave operation at 100 degrees C for 72 h shows almost no degradation, indicating the high crystal quality of the devices. |
| ISSN: 0256-307X |
| Article Number: 027801 |
| DOI: 10.1088/0256-307X/27/2/027801 |
| Record 13 of 15 |
| Author(s): Zhang, YX (Zhang Yun-Xiao); Pan, JQ (Pan Jiao-Qing); Zhao, LJ (Zhao Ling-Juan); Zhu, HL (Zhu Hong-Liang); Wang, W (Wang Wei) |
| Title: Design and Characterization of Evanescently Coupled Uni-Traveling Carrier Photodiodes with a Multimode Diluted Waveguide Structure |
| Source: CHINESE PHYSICS LETTERS, 27 (2): Art. No. 028501 FEB 2010 |
| Abstract: A new evanescently coupled uni-traveling carrier photodiode (EC-UTC-PD) is designed, fabricated and characterized, which incorporates a multimode diluted waveguide structure and UTC active waveguide structure together. A high responsivity of 0.68A/W at 1.55-mu m without an anti-reflection coating, a linear photocurrent responsivity of more than 21 mA, and a large-1 dB vertical alignment tolerance of 2.5 mu m are achieved. |
| ISSN: 0256-307X |
| Article Number: 028501 |
| DOI: 10.1088/0256-307X/27/2/028501 |
| Record 14 of 15 |
| Author(s): Che, KJ (Che, Kai-Jun); Yang, YD (Yang, Yue-De); Huang, YZ (Huang, Yong-Zhen) |
| Title: Multimode resonances in metallically confined square-resonator microlasers |
| Source: APPLIED PHYSICS LETTERS, 96 (5): Art. No. 051104 FEB 1 2010 |
| Abstract: Directional emission InP/AlGaInAs square-resonator microlasers with a side length of 20 mu m are fabricated by standard photolithography and inductively coupled-plasma etching technique. Multimode resonances with about seven distinct mode peaks in a free-spectral range are observed from 1460 to 1560 nm with the free-spectral range of 12.1 nm near the wavelength of 1510 nm, and the mode refractive index versus the photon energy E (eV) as 3.07152+0.18304E are obtained by fitting the laser spectra with an analytical mode wavelength formula derived by light ray method. In addition, mode field pattern is simulated for cold cavity by two dimensional finite-difference time-domain technique. |
| ISSN: 0003-6951 |
| Article Number: 051104 |
| DOI: 10.1063/1.3302406 |
| Record 15 of 15 |
| Author(s): Lu, QY (Lu, Quan-Yong); Guo, WH (Guo, Wan-Hong); Zhang, W (Zhang, Wei); Wang, LJ (Wang, Li-Jun); Liu, JQ (Liu, Jun-Qi); Li, L (Li, Lu); Liu, FQ (Liu, Feng-Qi); Wang, ZG (Wang, Zhan-Guo) |
| Title: Room temperature operation of photonic-crystal distributed-feedback quantum cascade lasers with single longitudinal and lateral mode performance |
| Source: APPLIED PHYSICS LETTERS, 96 (5): Art. No. 051112 FEB 1 2010 |
| Abstract: We demonstrate room temperature operation of photonic-crystal distributed-feedback quantum cascade lasers emitting at 4.7 mu m. A rectangular photonic crystal lattice perpendicular to the cleaved facet was defined using holographic lithography. The anticrossing of the index- and Bragg-guided dispersions of rectangular lattice forms the band-edge mode with extended mode volume and reduced group velocity. Utilizing this coupling mechanism, single mode operation with a near-diffractive-limited divergence angle of 12 degrees is obtained for 33 mu m wide devices in a temperature range of 85-300 K. The reduced threshold current densities and improved heat dissipation management contribute to the realization of devices' room temperature operation. |
| ISSN: 0003-6951 |
| Article Number: 051112 |
| DOI: 10.1063/1.3295704 |
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