|
|
Generalized Coherent States of a Particle in a Time-Dependent Linear Potential
L. Krache, M. Maamache, Y. Saadi, A. Beniaiche
Chin. Phys. Lett. 2009, 26 (7):
070307
.
DOI: 10.1088/0256-307X/26/7/070307
We derive, with an invariant operator method and unitary transformation approach, that the Schrödinger equation with a time-dependent linear potential possesses an infinite string of shape-preseving wave-packet states |φα,λ>(t)> having classical motion. The qualitative properties of the invariant eigenvalue spectrum (discrete or continuous) are described separately for the different values of the frequency ω of a harmonic oscillator. It is also shown that, for a discrete eigenvalue spectrum, the states |φα,n>(t)> could be obtained from the coherent state |φα,0>(t).
|
|
|
Phase Transition in CCl4 under Pressure: a Raman Spectroscopic Study
LIU Tie-Cheng, ZHOU Mi, GAO Shu-Qin, LI Zuo-Wei, LI Zhan-Long, ZHANGPeng, LI Liang, LV Tian-Quan, XU Da-Peng
Chin. Phys. Lett. 2009, 26 (7):
070701
.
DOI: 10.1088/0256-307X/26/7/070701
High-pressure Raman studies at room temperature are performed on CCl4 up to 13GPa. The Raman bands of the internal modes (v2, v4 and v1) show entirely positive pressure dependence. The slopes dω/dP of the internal modes exhibit two sudden changes at 0.73GPa and 7.13GPa, respectively. A new lower frequency mode (225cm-1) appears at 3.03GPa, and the splitting of v2, ν3 and v4 occurs at about 7.13GPa. Moreover, Raman spectra of Fermi
resonance show that the relative position of the v1 + v4 combination and the ν3 fundamental firstly interchanges corresponding to that at ambient pressure, then the v1 +v4 combination disappears in the gradual process of compression. It is indicated that the pressure-induced phase transition from CCl4 II to CCl4 III occurs at 0.73GPa, and CCl4 III undergoes a transition to CCl4 IV below 3.03GPa. Further CCl4 IV transforms in a new high-pressure phase at about 7.13GPa, and the symmetry of the new high-pressure phase is lower than that of CCl4 IV. All the transitions are reversible during decompression.
|
|
|
Theoretical Analysis and New Formulae for Half-Lives of Proton Emission
ZHANG Hong-Fei, DONG Jian-Min, WANG Yan-Zhao, SU Xin-Ning, WANG Yong-Jia, CAI Ling-Zhi, ZHU Tian-Bao, HU Bi-Tao, ZUO Wei, LI Jun-Qing,
Chin. Phys. Lett. 2009, 26 (7):
072301
.
DOI: 10.1088/0256-307X/26/7/072301
The proton radioactivity half-lives of spherical proton emitters are calculated by the cluster model with the contribution of a centrifugal potential barrier considered separately. The results are compared with the experimental data and other theoretical data, and good agreement is found for most nuclei. In addition, two formulae are proposed for the proton decay half-life of spherical proton emitters through the least squares fit to the experimental data available, and could reproduce the experimental half-lives successfully.
|
|
|
Angular Distribution of the 12C(6He, 7Li)11B Reaction
LI Er-Tao, LI Zhi-Hong, LI Yun-Ju, YAN Sheng-Quan, BAI Xi-Xiang, GUOBing, SU Jun, WANG You-Bao, WANG Bao-Xiang, LIAN Gang, ZENGSheng, FANG Xiao, ZHAO Wei-Juan, LIU Wei-Ping
Chin. Phys. Lett. 2009, 26 (7):
072401
.
DOI: 10.1088/0256-307X/26/7/072401
Angular distribution of the 12C(6He,7Li)11B transfer reaction is measured with a secondary 6He beam of 36.4MeV for the first time. The experimental angular distribution is well reproduced by the distorted-wave Born approximation (DWBA) calculation. The success of the present experiment shows that it is feasible to measure one-nucleon transfer reaction on a light nucleus target with the secondary beam facility of the HI-13 tandem accelerator at China Institute of Atomic Energy (CIAE), Beijing.
|
|
|
In-Situ Characterization of Three-Dimensional Optical Matters by Light Diffraction
JIANG Lai-Dong, DAI Qiao-Feng, FENG Tian-Hua, LIU Jin, WU Li-Jun, LAN Sheng, A. V. Gopal, V. A. Trofimov
Chin. Phys. Lett. 2009, 26 (7):
074201
.
DOI: 10.1088/0256-307X/26/7/074201
Three-dimensional optical matters are created by combining the single beam optical trapping with the conventional Z-scan technique. Dynamic light diffraction is employed to evaluate the structure and quality of the optical matter formed at the optimum trapping power. The lattice constant of the optical matter is extracted based on the Bragg and Snell laws, showing that polystyrene spheres are nearly close-packed in the optical matter, confirmed by comparing the diffraction pattern of the optical matter with that of a colloidal photonic crystal fabricated by the self-assembled technique. The relatively broad diffraction peaks observed in the optical matter indicate that the density of disorders in it is higher than that in the photonic crystal. It is suggested that the optical matter possesses a random close-packed structure rather than a face centered cubic one.
|
|
|
Design and Fabrication of an Er-Doped Silica Optical Fiber with Six Photosensitive Subcores
LI Jian, , WANG Jing, LIU Peng, , LU Shao-Hua, MAO Xiang-Qiao, JIANG Wei-Wei, NING Ti-Gang, JIAN Shui-Sheng,
Chin. Phys. Lett. 2009, 26 (7):
074209
.
DOI: 10.1088/0256-307X/26/7/074209
A type of multi-core Er-doped photosensitive silica optical fiber (MC-EDPF) is proposed and fabricated, in which a high consistency Er-doped core is surrounded by six high consistency Ge-doped cores. The multi-core design can overcome the difficulties encountered in the design and fabrication of single-core EDPFs through a modified chemical vapor deposition method combined with solution doping technology, and there is a conflict between high consistency Er doping and high consistency Ge doping. The absorption of MC-EDPFs achieved 15.876dB/m at 1550nm and 10dB/m at 980nm. The reflectivity of the fiber Bragg gratings (FBGs) written directly on the MC-EDPFs is as much as 96.84%.
|
|
|
The Phase Transition of Eu2O3 under High Pressures
JIANG Sheng, BAI Li-Gang, LIU Jing, XIAO Wan-Sheng, LI Xiao-Dong, LI Yan-Chun, TANG Ling-Yun, ZHANG Yu-Feng, ZHANG De-Chun, ZHENG Li-Rong
Chin. Phys. Lett. 2009, 26 (7):
076101
.
DOI: 10.1088/0256-307X/26/7/076101
Pressure-induced phase transition of cubic Eu2O3 is studied by angle-dispersive x-ray diffraction (ADXD) up to 42.3GPa at room temperature. A structural transformation from a cubic phase to a hexagonal phase is observed, which starts at 5.0GPa and finishes at about 13.1GPa. The phase transition leads to a volume collapse of 9.0% at 8.6GPa. The hexagonal phase of Eu2O3 maintains stable up to the highest experiment pressure. After release of pressure, the high-pressure phase transforms to a monoclinic phase. The pressure-volume data are fitted with the Birch-Murnaghan equation of state. The bulk moduli obtained upon compression from the fitting are 145(2)GPa and 151(6)GPa for the cubic and hexagonal phases, respectively, when their first pressure derivatives are fixed at 4.
|
|
|
Curvature and Hybridization Effects on the Persistent Current of a Carbon Nanotorus
XU Ning, DING Jian-Wen, CHEN Hong-Bo, MA Ming-Ming
Chin. Phys. Lett. 2009, 26 (7):
076102
.
DOI: 10.1088/0256-307X/26/7/076102
To accurately describe the persistent current for various toroidal carbon nanotubes (TCNs), a semiempirical sp3 tight-binding model is presented, in which the intrinsic curvature and hybridization have been fully taken into account. The calculations show that the curvature and hybridization can induce dramatic changes in the energy spectra of TCNs such as the Fermi energy EF shifting up, an energy gap opening at EF, and the energy spectrum symmetry about EF destroyed, which leads to a decrease of persistent current and changes in the shape of the flux-dependent current. In the presence of curvature and hybridization, the persistent current in non-armchair TCNs is nearly an order of magnitude lower than that obtained by using the Brillouin-zone folding approach, while it is of the same order of magnitude in armchair TCNs.
|
|
|
Curvature Correction of FWHM in the X-Ray Rocking Curve of Bent Heteroepitaxial Films
WANG Liang-Ji, ZHANG Shu-Ming, WANG Yu-Tian, JIANG De-Sheng, ZHU Jian-Jun, ZHAO De-Gang, LIU Zong-Shun, WANG Hui, SHI Yong-Sheng, WANG Hai, LIU Su-Ying, YANG Hui,
Chin. Phys. Lett. 2009, 26 (7):
076104
.
DOI: 10.1088/0256-307X/26/7/076104
A method for accurate determination of the curvature radius of semiconductor thin films is proposed. The curvature-induced broadening of the x-ray rocking curve (XRC) of a heteroepitaxially grown layer can be determined if the dependence of the full width at half maximum (FWHM) of XRC is measured as a function of the width of incident x-ray beam. It is found that the curvature radii of two GaN films grown on a sapphire wafer are different when they are grown under similar MOCVD conditions but have different values of layer thickness. At the same time, the dislocation-induced broadening of XRC and thus the dislocation density of the epitaxial film can be well calculated after the curvature correction.
|
|
|
Orientation and Rate Dependence of Wave Propagation in Shocked Beta-SiC from Atomistic Simulations
CHENG Qin, WU Heng-An, WANG Yu, WANG Xiu-Xi
Chin. Phys. Lett. 2009, 26 (7):
076202
.
DOI: 10.1088/0256-307X/26/7/076202
The orientation dependence of planar wave propagation in beta-SiC is studied via the molecular dynamics (MD) method. Simulations are implemented under impact loadings in four main crystal directions, i.e., <100>, <110>, <111>, and <112>. The dispersion of stress states in different directions increases with rising impact velocity, which implies the anisotropic characteristic of shock wave propagation for beta-SiC materials. We also obtain the Hugoniot relations between the shock wave velocity and the impact velocity, and find that the shock velocity falls into a plateau above a threshold of impact velocity. The shock velocity of the plateaux is dependent on the shock directions, while <111> and <112> can be regarded as equivalent directions as they almost reach the same plateau. A comparison between the atomic stress from MD and the stress from Rankine-Hugoniot jump conditions is also made, and it is found that they agree with each other very well.
|
|
|
Low-Energy Collective Excitation of Bose-Einstein Condensates in an Anisotropic Magnetic Trap
YANG Lu, WANG Xiao-Rui, LI Ke, TAN Xin-Zhou, XIONG Hong-Wei, LU Bao-Long
Chin. Phys. Lett. 2009, 26 (7):
076701
.
DOI: 10.1088/0256-307X/26/7/076701
We experimentally investigate the collective excitation of 87Rb Bose-Einstein condensates confined in a cigar-shaped magnetic trap (QUIC trap). Using a method of magnetic perturbation, the center-of-mass oscillation of the condensate is excited, so that the radial trapping frequency of the QUIC trap can be precisely determined. A high-order excitation, characterized by a fast shape oscillation, also occurs simultaneously, with a noticeable damping in the oscillation amplitude compared with the oscillation of the center of mass. The measured oscillation frequencies, associated with these two low-energy excitation modes, agree well with theoretical predictions based on the Gross-Pitaevskii equation.
|
|
|
Density Functional Calculation of the 0.5ML-Terminated Allyl Mercaptan/Si(100)-(2×1) Surface
TANG Chun-Mei, DENG Kai-Ming, CHEN Xuan, XIAO Chuan-Yun, LIU Yu-Zhen, LI Qun-Xiang
Chin. Phys. Lett. 2009, 26 (7):
076801
.
DOI: 10.1088/0256-307X/26/7/076801
The structural and electronic properties of the 0.5ML-terminated allyl mercaptan (ALM)/Si(100)-(2×1) surface are studied using the density functional method. The calculated absorption energy of the ALM molecule on the 0.5ML-terminated ALM/Si(100)-(2×1) surface is 3.36eV, implying that adsorption is strongly favorable. The electronic structure calculations show that the ALM/Si(100)-(2×1), the clean Si(100)-(2×1), and the fully-terminated H/Si(100)-(2×1) surfaces have the nature of an indirect band gap semiconductor. The highest occupied molecular orbital is dominated by the ALM, confirming the mechanism proposed by Hossain for its chain reaction.
|
|
|
Halopentacenes: Promising Candidates for Organic Semiconductors
DU Gong-He, REN Zhao-Yu, GUO Ping, ZHENG Ji-Ming
Chin. Phys. Lett. 2009, 26 (7):
077101
.
DOI: 10.1088/0256-307X/26/7/077101
We introduce polar substituents such as F, Cl, Br into pentacene to enhance the dissolubility in common organic solvents while retaining the high charge-carrier mobilities of pentacene. Geometric structures, dipole moments, frontier molecule orbits, ionization potentials and electron affinities, as well as reorganization energies of those molecules, and of pentacene for comparison, are successively calculated by density functional theory. The results indicate that halopentacenes have rather small reorganization energies (<0.2eV), and when the substituents are in position 2 or positions 2 and 9, they are polarity molecules. Thus we conjecture that they can easily be dissolved in common organic solvents, and are promising candidates for organic semiconductors.
|
|
|
First-Principles Study of Structural Stabilities, Electronic and Optical Properties of SrF2 under High Pressure
HAO Ai-Min, YANG Xiao-Cui, LI Jie, XIN Wei, ZHANG Su-Hong, ZHANG Xin-Yu, LIU Ri-Ping
Chin. Phys. Lett. 2009, 26 (7):
077103
.
DOI: 10.1088/0256-307X/26/7/077103
An investigation of structural stabilities, electronic and optical properties of SrF2 under high pressure is conducted using a first-principles calculation based on density functional theory (DFT) with the plane wave basis set as implemented in the CASTEP code. Our results predict that the second high-pressure phase of SrF2 is of a Ni2In-type structure, and demonstrate that the sequence of the pressure-induced phase transition of SrF2 is the fluorite structure (Fm3m) to the PbCl2-type structure (Pnma), and to the Ni2In-type phase (P63/mmc). The first and second phase transition pressures are 5.77 and 45.58GPa, respectively. The energy gap increases initially with pressure in the Fm3m, and begins to decrease in the Pnma phases at 30GPa. The band gap overlap metallization does not occur up to 210GPa. The pressure effect on the optical properties is discussed.
|
|
|
Electric Field Control of Interface Related Spin Splitting in Step Quantum Wells
HAO Ya-Fei, CHEN Yong-Hai, HAO Guo-Dong, WANG Zhan-Guo
Chin. Phys. Lett. 2009, 26 (7):
077104
.
DOI: 10.1088/0256-307X/26/7/077104
Spin splitting of the AlyGa1-yAs/GaAs/AlxGa1-xAs/AlyGa1-yAs (x≠y) step quantum wells (QWs) has been theoretically investigated with a model that includes both the interface and the external electric field contribution. The overall spin splitting is mainly determined by the interface contribution, which can be well manipulated by the external electric field. In the absence of the electric field, the Rashba effect exists due to the internal structure inversion asymmetry (SIA). The electric field can strengthen or suppress the internal SIA, resulting in an increase or decrease of the spin splitting. The step QW, which results in large spin splitting, has advantages in applications to spintronic devices compared with symmetrical and asymmetrical QWs. Due to the special structure design, the spin splitting does not change with the external electric field.
|
|
|
Effect of Tunneling Current on Schottky Barrier Height in ZnO Varistors at Low Temperature
LI Sheng-Tao, YANG Yan, ZHANG Le, CHENG Peng-Fei, LI Jian-Ying
Chin. Phys. Lett. 2009, 26 (7):
077201
.
DOI: 10.1088/0256-307X/26/7/077201
On the basis of the Schottky barrier and thermionic emission models, the temperature dependence of barrier height in ZnO varistors is investigated by the I-V characteristics in a wide temperature range from 93K to 373K. The obtained barrier height decreases with reducing temperature, which is ascribed to the contribution of tunneling current in measured current. From the proposed equivalent circuit, it is suggested that two current components coexist. One is thermionic emission current, which reflects the thermionic emission barrier height. The other is tunneling current, which appears even at low voltage, especially in low temperature ranges, and thus makes the barrier height obtained from measured current vary with temperature.
|
|
|
Field-Effect Transistor Based on Si with LaAlO3-δ as the Source and Drain
YANG Fang, JIN Kui-Juan, LU Hui-Bin, HE Meng, YANG Guo-Zhen
Chin. Phys. Lett. 2009, 26 (7):
077301
.
DOI: 10.1088/0256-307X/26/7/077301
N-type LaAlO3-δ thin films are epitaxially grown on p-type Si substrates. An enhancement mode field-effect transistor is constructed with oxygen deficient LaAlO3-δ as the source and drain, p-type Si as the semiconducting channel, and SiO2 as the gate insulator, respectively. The typical current-voltage behavior with field-effect transistor characteristic is observed. The ON/OFF ratio reaches 14at a gate voltage of 10V, the field-effect mobility is 10cm2/V・s at a gate voltage of 2V, and the transconductance is 5×10-6 A/V at a drain-source voltage of 0.8V at room temperature. The present field-effect transistor device demonstrates the possibility of realizing the integration of multifunctional perovskite oxides and the conventional Si semiconductor.
|
|
|
A Physics-Based Charge-Control Model for InP DHBT Including Current-Blocking Effect
GE Ji, JIN Zhi, SU Yong-Bo, CHENG Wei, WANG Xian-Tai, CHEN Gao-Peng, LIU Xin-Yu
Chin. Phys. Lett. 2009, 26 (7):
077302
.
DOI: 10.1088/0256-307X/26/7/077302
We develop a physics-based charge-control InP double heterojunction bipolar transistor model including three important effects: current blocking, mobile-charge modulation of the base-collector capacitance and velocity-field modulation in the transit time. The bias-dependent base-collector depletion charge is obtained analytically, which takes into account the mobile-charge modulation. Then, a measurement based voltage-dependent transit time formulation is implemented. As aresult, over a wide range of biases, the developed model shows good agreement between the modeled and measured S-parameters and cutoff frequency. Also, the model considering current blocking effect demonstrates more accurate prediction of the output characteristics than conventional vertical bipolar inter company results.
|
|
|
Transition of Magnetoresistance in Co/Alq3 Granular Film on Silicon Substrate
SHU Qi, ZHAO Xiao-Meng, ZHANG Yan, SHENG Peng, TANG Zhen-Yao, NI Gang,
Chin. Phys. Lett. 2009, 26 (7):
077505
.
DOI: 10.1088/0256-307X/26/7/077505
A Co0.38(Alq3)0.62 granular film is prepared using a co-evaporating technique on a silicon substrate with a native oxide layer. A crossover of magnetoresistance (MR) from positive to negative is observed. The positive MR ratio reaches 17.5% at room temperature (H=50 kOe), and the negative MR ratio reaches -1.35% at 15K (H=10 kOe). Furthermore, a metal-insulator transition is also observed. The transition of resistance and MR results from the channel switching of electron transport between the upper Co-Alq3
granular film and the inversion layer underneath. The negative MR originates from the tunneling magnetoresistance effect due to the tunneling conducting between adjacent Co granules, and the positive MR may be attributed to the transport of high mobility carriers in the SiO2/Si inversion layer.
|
|
|
Optical Characterization of rf-Magnetron Sputtered Nanostructured SnO2 Thin Films
Abdul Faheem Khan, Mazhar Mehmood, A. M. Rana, M. T. Bhatti, A. Mahmood
Chin. Phys. Lett. 2009, 26 (7):
077803
.
DOI: 10.1088/0256-307X/26/7/077803
Tin oxide (SnO2) thin films are deposited by rf-magnetron sputtering and annealed at various temperatures in the range of 100-500°C for 15min. Raman spectra of the annealed films depict the formation of a small amount of SnO phase in the tetragonal SnO2 matrix, which is verified by x-ray diffraction. The average particle size is found to be about 20-30nm, as calculated from x-ray peak broadening and SEM images. Various optical parameters such as optical band gap energy, refractive index, optical conductivity, carrier mobility, carrier concentration etc. are determined from the optical transmittance and reflectance data recorded in the wavelength range 250-2500nm. The results are analyzed and compared with the data in the literature.
|
|
|
Nondoped Electrophosphorescent Organic Light-Emitting Diodes Based on Platinum Complexes
YANG Gang, ZHANG Di, WANG Jun, JIANG Quan, ZHONG Jian, YUJun-Sheng, ZHU Feng-Zhi, LUO Kai-Jun, XIE Yun, XU Ling-Ling
Chin. Phys. Lett. 2009, 26 (7):
077804
.
DOI: 10.1088/0256-307X/26/7/077804
An undoped electrophosphorescent organic light-emitting diode is fabricated using a pure platinum(II) (2-phenylpyridinato-N, C2) (3-benzoyl-camphor) [(ppy)pt(bcam)] phosphorescent layer acting as the emitting layer. A maximum power efficiency ηp of 6.62lm/W and current efficiency of 14.78cd/A at 745cd/m2 are obtained from the device. The roll-off percentage of ηp of the pure phosphorescent phosphor layer device is reduced to 5% at a current density of 20mA/cm2, which is about 11% for conventional phosphorescent devices. The low roll-off efficiency is attributed to the phosphorescent material, which has the molecular structure of a strong steric hindrance effect.
|
|
|
Optical Dispersion Behavior and Band Gap Energy of Relaxor Ferroelectric 0.92Pb(Mg1/3Nb2/3)O3-0.08PbTiO3 Single Crystal
LIN Yan-Ting, REN Bo, ZHAO Xiang-Yong, WANG Fei-Fei, WANG Yao-Jin, XU Hai-Qing, LIN Di, LUO Hao-Su
Chin. Phys. Lett. 2009, 26 (7):
077807
.
DOI: 10.1088/0256-307X/26/7/077807
Refractive indices and extinction coefficients of 0.92Pb(Mg1/3Nb2/3)O3-0.08PbTiO3(PMN-0.08PT) single crystal are investigated by variable angle spectroscopic ellipsometry (VASE) at different wavelengths. The parameters relative to the energy band structure are obtained by fitting to the single-oscillator dispersion equation, and the band gap energy is also deduced from the Tauc equation. Similar to most oxygen-octahedra ferroelectrics, PMN-0.08PT has the same dispersion behavior described by the refractive-index dispersion parameters.
|
|
|
Structural and Photoluminescence Properties for Highly Strain-Compensated InGaAs/InAlAs Superlattice
GU Yi, ZHANG Yong-Gang, LI Ai-Zhen, WANG Kai, LI Cheng, LIYao-Yao
Chin. Phys. Lett. 2009, 26 (7):
077808
.
DOI: 10.1088/0256-307X/26/7/077808
The effects of strain compensation are investigated by using twenty periods of highly strain-compensated InGaAs/InAlAs superlattice. The lattice mismatches of individual layers are as high as about 1%, and the thicknesses are close to critical thicknesses. X-ray diffraction measurements show that lattice imperfectness is not serious but still present, though the structural parameters are within the range of theoretical design criteria for structural stability. Rough interfaces and composition fluctuations are the primary causes for lattice imperfectness. Photoluminescence measurements show the large thermally activated nonradiative recombination in the sample. In addition, the recombination process gradually evolves from excitonic recombination at lower temperatures to band-to-band recombination at higher temperatures, which should be considered in device applications.
|
|
|
Efficient White Light Emission Using a Single Copolymer with Red and Green Chromophores on a Conjugated Polyfluorene Backbone Hybridized with InGaN-Based Light-Emitting Diodes
ZHANG Yong, HOU Qiong, NIU Qiao-Li, ZHENG Shu-Wen, LI Shu-Ti, HE Miao, FAN Guang-Han
Chin. Phys. Lett. 2009, 26 (7):
077811
.
DOI: 10.1088/0256-307X/26/7/077811
We report an efficient white-light emission based on a single copolymer/InGaN hybrid light-emitting diode. The single copolymer consists of a conjugated polyfluorene backbone by incorporating 2,1,3-benzothiadiazole (BT) and 4,7-bis(2-thienyl)-2,1,3-benzothiadiazole (DBT) as green and red light-emitting units, respectively. For the single copolymer/InGaN hybrid device, the Commission Internationale de l'Eclairage (CIE) coordinates, color temperature Tc and color rendering index Ra at 20mA are (0.323,0.329), 5960K and 86, respectively. In comparison with the performance of red copolymer PFO-DBT15 (DOF:DBT=85:15 with DOF being 9'9-dioctylfluorene) and green copolymer PFO-BT35 (DOF:BT=65:35) blend/InGaN hybrid white devices, it is concluded that the chemically doped copolymer hybridized device shows a higher emission intensity and spectral stability at a high driving current than the polymer blend.
|
|
|
Wavelength Red-Shift of Long Wavelength InGaN/GaN Multi-Quantum Well by Using an InGaN Underlying Layer
HUANG Li-Rong, WEN Feng, TONG Liang-Zhu, HUANG De-Xiu
Chin. Phys. Lett. 2009, 26 (7):
078502
.
DOI: 10.1088/0256-307X/26/7/078502
Long-wavelength GaN based light-emitting diodes are of importance in full color displays, monolithic white light-emitting diodes and solid-state lighting, etc. However, their epitaxial growth faces great challenges because high indium (In) compositions of InGaN are difficult to grow. In order to enhance In incorporation and lengthen the emission wavelength of a InGaN/GaN multi-quantum well (MQW), we insert an InGaN underlying layer underneath the MQW. InGaN/GaN MQWs with various InGaN underlying layers, such as graded InyGa1-yN material with linearly increasing In content, or InyGa1-yN with fixed In content but different thicknesses, are grown by metal-organic chemical vapor deposition. Experimental results demonstrate the enhancement of In incorporation and the emission wavelength redshift by the insertion of an InGaN underlying layer.
|
|
|
Withdrawal of Chinese Physics Letters 26 (2009) 016104 "In Situ Tests of Multiwalled Carbon Nanotubes with Strength Close to Theoretical Predictions"by Peng Bei et al.
Chin. Phys. Lett. 2009, 26 (7):
079901
.
DOI: 10.1088/0256-307X/26/7/079901
This paper has been retracted, as requested by Chinese Physics Letters, because of its substantial replication of an earlier paper, 'Measurements of near-ultimate strength for multiwalled carbon nanotubes and irradiation-induced crosslinking improvements' by Peng B et al., which appeared in Nature Nanotechnology 3(2008)626.I alone, as the first author of the paper, was responsible for this misconduct. Therefore, I would like to express my deepest apology to Professor Horacio Espinosa whose name was included in the above referenced paper without his knowledge, and to both journals, Chinese Physics Letters and Nature Nanotechnology.
|
108 articles
|