Junbo Li
Chinese Academy of Sciences
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Publication
Featured researches published by Junbo Li.
Journal of Organic Chemistry | 2008
Mingjian Yuan; Weidong Zhou; Xiaofeng Liu; Mei Zhu; Junbo Li; Xiaodong Yin; Haiyan Zheng; Zicheng Zuo; Canbin Ouyang; Huibiao Liu; Yuliang Li; Daoben Zhu
A novel fluorescent probe that possess both BODIPY and Rhodamine moieties has been designed for the selective detection of Hg(2+) and Ba(2+) ions on the controlling by a logic gate. The characteristic fluorescence of the Ba(2+)-selective OFF-ON and the Hg(2+)-selective fluorescence bathochromic shift can be observed, and the concept has been used to construct a combinational logic circuit at the molecular level. These results will be useful for further molecular design to mimic the function of the complex logic gates on controlling.
Applied Physics Letters | 1999
Hui Yang; Lianxi Zheng; Junbo Li; Xinzhong Wang; Duanfu Xu; Y.T. Wang; Xueda Hu; P. D. Han
The feasibility of growing device-quality cubic GaN/GaAs(001) films by metal organic chemical vapor deposition has been demonstrated. The optical quality of the GaN films was characterized by room-temperature photoluminescence measurements, which shows a full width at half maximum of 46 meV. The structural quality of the films was investigated by transmission electron microscopy. There are submicron-size grains free from threading dislocations and stacking faults. More importantly, a cubic-phase GaN blue light-emitting diode has been fabricated. The device process, which is very simple and compatible with current GaAs technology, indicates a promising future for the blue light-emitting diode
Nanotechnology | 2007
Huibiao Liu; Junbo Li; Changshi Lao; Changshui Huang; Yuliang Li; Zhong Lin Wang; Daoben Zhu
We report the synthesis of small-molecule organic conductor nanowires of TTF-TCNQ by selective inducement in a two-phase method by pi-pi stacking interaction. The morphologies of TTF-TCNQ, from straight nanowires to helical nanowires and to complicated helical dendrite structures, have been controlled by adjusting the experimental conditions. The technique has been applied to the synthesis of AgTCNQ/CuTCNQ nanowires in a two-phase system of acetonitrile/hexane. I-V characterization of an individual nanowire indicated that the conductivity along the b-axis of the TTF-TCNQ helical nanowire is much better than that along other directions. The synthetic procedure presented is a general approach for producing controlled organic conductor/semiconductor nanowires.
Applied Physics Letters | 1999
X. L. Sun; Hui Yang; Liu Zheng; Duanfu Xu; Junbo Li; Yuren Wang; Guihua Li; Z.G. Wang
The thermal stability of cubic-phase GaN (c-GaN) films are investigated by photoluminescence (PL) and Raman scattering spectroscopy. C-GaN films are grown on GaAs (001) substrates by metalorganic chemical vapor deposition. PL measurements show that the near-band-edge emissions in the as-grown GaN layers and thermally treated samples are mainly from c-GaN. No degradation of the optical qualities is observed after thermal annealing. Raman scattering spectroscopy shows that the intensity of the E-2 peak from hexagonal GaN grains increases with annealing temperature for the samples with poor crystal quality, while thermal annealing up to 1000 degrees C has no obvious effect on the samples with high crystal quality
Applied Physics Letters | 2000
Dapeng Xu; Hui Yang; Junbo Li; D. G. Zhao; S.F Li; S. M. Zhuang; R. H. Wu; Y. Chen; Guihua Li
The optical properties of cubic GaN films have been investigated in the temperature range of 10–300 K. Five peaks were observed at 10 K. From the dependence of photoluminescence emissions on the temperature and excitation intensity, we have assigned two of the five peaks (2.926 and 2.821 eV) to donor–acceptor pair (DAP) transitions. Furthermore, these two peaks were found to be related to a common shallow donor involved in the peak position previously reported at 3.150 eV. The intensities of DAP transitions were much weaker than that of excitonic emission even at low temperature, indicating a relatively high purity of our samples.
Thin Solid Films | 2000
Xilian Sun; Y.T. Wang; Hui Yang; Junbo Li; Lianxi Zheng; Duanfu Xu; Z. G. Wang
Cubic GaN(c-GaN) films are grown on GaAs(001) substrates by metalorganic chemical vapor deposition (MOCVD). Two GaN samples were grown with different buffer layer, the deposition time of each was 1 and 3 min, respectively. 4-circle X-ray double crystal diffraction (XRDCD) was used to study the secondary crystallographic phases presented in the c-GaN films. The phase composition of the epilayers was determined by X-ray reciprocal space mapping. The intensities of the c-GaN(002) and h-GaN(10 (1) over bar 1) planes detected in the mapping were investigated by omega scans. The content of the hexagonal phase inclusions in the c-GaN films was calculated to about 1.6 and 7.9%, respectively. The thicker buffer layer is not preferable for growing high quality pure c-GaN films
Applied Physics Letters | 1999
D. G. Zhao; D. S. Jiang; Hui Yang; Lianxi Zheng; Duanfu Xu; Junbo Li; Qisheng Wang
We have studied the photovoltaic effect in cubic GaN on GaAs at room temperature. The photovoltaic spectra of cubic GaN epitaxial film were concealed by the photovoltaic effect from the GaAs substrate unless additional illumination of a 632.8 nm He-Ne laser beam was used to remove the interference of the GaAs absorption in the measurement. On the basis of the near-band-edge photovoltaic spectra of cubic GaN, we obtained the minority carrier diffusion lengths of about 0.32 and 0.14 mu m for two undoped n-type cubic GaN samples with background concentrations of 10(14) and 10(18) cm(-3), respectively
Thin Solid Films | 1998
Lianxi Zheng; Hai-Bo Yang; Duanfu Xu; Xinzhong Wang; Xuegang Li; Junbo Li; Y.T. Wang; Lina Duan; Xueda Hu
Low-temperature growth of cubic GaN at 520 degrees C was achieved using CCl4 as an additive by metalorganic chemical-vapor deposition (MOCVD) on GaAs substrate. X-Ray measurement confirmed that the films are single-phase cubic GaN. Scanning electron microscopy (SEM) and reflection high-energy electron diffraction (RHEED) were also used to analyze the surface morphology and the quality of films. The evolution of surface morphology suggests that CCl4 can reduce the hopping barrier and thus Ga adatoms are able to diffuse easily on the GaN surface
MRS Proceedings | 1998
Junbo Li; Hui Yang; Lianxi Zheng; Duanfu Xu; Y.T. Wang
We report on the growth of high-quality cubic phase InGaN on GaAs by MOCVD. The cubic InGaN layers are grown on cubic GaN buffer layers on GaAs (001) substrates. The surface morphology of the films are mirror-like. The cubic nature of the InGaN films is obtained by Xray diffraction (XRD) measurements. The InGaN layers show strong photoluminescence (PL) at room temperature. Neither emission peak from wurtzite GaN nor yellow luminescence is observed in our films. The highest In content as determined by XRD is about 17% with an PL emission wavelength of 450 nm. The FWHM of the cubic InGaN PL peak are 153 meV and 216 meV for 427 nm and 450 nm emissions, respectively. It is found that the In compositions determined from XRD are not in agreement with those estimated from PL measurements. The reasons for this disagreement are discussed.
Thin Solid Films | 2000
Dapeng Xu; Hui Yang; Junbo Li; S.F Li; D. G. Zhao; Y.T. Wang; Xilian Sun; R. H. Wu
We present some results on the effect of initial buffer layer on the crystalline quality of Cubic GaN epitaxial layers grown on GaAs(100) substrates by metalorganic chemical vapor deposition. Photoluminescence and Hall measurements were performed to characterize the electrical and optical properties of cubic GaN. The crystalline quality subsequently grown high-temperature (HT) cubic GaN layers strongly depended on thermal effects during the temperature ramping process after low temperature (LT) growth of the buffer layers. Atomic force microscope (AFM) and reflection high-energy electron diffraction (RHEED) were employed to investigate this temperature ramping process. Furthermore, the role of thermal treatment during the temperature ramping process was identified. Using the optimum buffer layer, the full width at half maxim (FWHM) at room temperature photoluminescence 5.6 nm was achieved. To our knowledge, this is the best FWHM value for cubic GaN to date. The background carrier concentration was as low as 3 x 10(13) cm(-3)