Xiang Wang

Hanshan Normal University, Ch’ao-chou-chen, Guangdong, China

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Publications (52)109.61 Total impact

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    ABSTRACT: Amorphous silicon oxycarbide (a-SiCxOy) films that displayed blue luminescence were fabricated using very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) at a temperature of 250°C. The effects of thermal annealing on the photoluminescence (PL) were investigated. Thermal annealing at 600°C resulted in a remarkable enhancement in the blue PL, which was clearly observed with the naked eyes in a bright room. The blue PL featured an excitation wavelength independent recombination dynamic on a nanosecond timescale. Neither Si nor SiC quantum dots were present in the annealed films as revealed by transmission electron microscopy. The PL results, combined with an analysis of the chemical bonds present in the films, revealed that the origin of the blue PL was largely due to electron-hole pair recombination through Si-related neutral oxygen vacancy defect centers.
    No preview · Article · Nov 2015 · Journal of Non-Crystalline Solids
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    ABSTRACT: Lightly doped hydrogenated amorphous silicon thin films were deposited through the plasma enhanced chemical vapor deposition (PECVD) technique using a gas mixture of SiH4, B2H6, and H2 as the precursor. By using thermal annealing at 800 and 1000°C, boron doped nanocrystalline silicon films were obtained. X-ray photoelectron spectroscopy (XPS) measurements demonstrated the presence of substitutional boron in the doped films. Based on the measurement of dark conductivity as a function of temperature, p-type nanocrystalline silicon (nc-Si:H) films with high room temperature conductivity and low active energy were observed. By using these p-type silicon films, P-N junction solar cells were prepared on the n-type nc-Si substrate. The device characteristics were investigated based on the measurements of the current-voltage and spectral-response.
    No preview · Article · Sep 2015
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    ABSTRACT: Luminescent a-SiCxOy films were prepared at a low temperature of 150 °C by using very high frequency plasma enhanced chemical vapor deposition technique. The prepared a-SiCxOy films present remarkable photoluminescence with yellow to blue shifting emission when increasing the oxygen content from 29% to 44%. Interestingly, the light emissions in the visible region can be clearly observed with the naked eyes in a bright room. The structure and the chemical compositions of the films were further investigated by Raman spectroscopy and Fourier transform infrared absorption spectroscopy, respectively. Based on the PL results and the analyses of the bonding configurations of the films, the yellow emission is suggested from the SiC related defect luminescent centers, while the blue emission is associated with Si-related oxygen defect luminescent centers.
    No preview · Article · Jun 2015 · Journal of Alloys and Compounds
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    ABSTRACT: Silicon nitride-based light-emitting devices were fabricated with a SiNx emitting layer grown on annealed Si film of dense nano-crystalline cones. Comparative studies revealed that the patterned SiNx emitting layer, with embedding nanocrystalline Si cones and a rough surface morphology of its own, manifests a much enhanced, even doubled at sufficiently large injected current density, electroluminescence efficiency. Both the increased light-extraction capability and the effective hole-blocking by the presence of Si nanocones, the latter is favorable for the balance of carrier injection in emitting layer, are responsible for this remarkable efficiency enhancement. The current work established an alternative approach toward the fabrication of more efficient SiN-based light-emitting devices.
    No preview · Article · May 2015 · Optical Materials Express
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    ABSTRACT: We present an effective method to suppress the hole overflow in Si quantum dots-based silicon nitride (SiN) light-emitting diodes (LEDs) by employing nanocrystalline Si (nc-Si) layer as hole blocking layer inserted between the SiN luminescent active layer and p-Si anode. The proposed devices exhibit strong white light emission under forward bias conditions. In comparison to the LEDs without nc-Si interlayer, a significant enhancement of more than 200% in light emission efficiency is achieved from the proposed devices. The increment in EL efficiency is found to strongly depend on the thickness of nc-Si interlayer. Besides, the proposed devices show a low turn-on voltage of 6 V, which is the same as that of the device without nc-Si interlayer. The analysis of the dominant recombination process indicates that the improved emission efficiency is resulting from the increased bimolecular radiative recombination probability, which is attributed to the effective hole-blocking effect of nc-Si barrier that mitigates the unbalance injections between electrons and holes in the SiN active layer by suppressing hole overflow.
    No preview · Article · Jul 2014 · IEEE Journal of Selected Topics in Quantum Electronics
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    ABSTRACT: Near-infrared (NIR) luminescent Si-rich oxynitride nanostructures were fabricated by very high frequency plasma enhanced chemical vapor deposition followed by thermal annealing. By increasing the annealing temperature from 600 °C to 1100 °C, the intensity of NIR emission can be remarkably improved by more than three times. Si nanocrystals (NCs) with diameters ranging from 2 nm to 4 nm are found to play a decisive role in the enhanced NIR emission. The PLE spectra indicate a band-to-band excitation process with a quantum confinement feature in Si nanocrystals. Combining with the infrared absorption spectra and X-ray photoelectron spectra analyses, it is suggested that the photoexcited carriers for the enhanced NIR emission mainly originate in the quantum confined Si NCs, while their radiative recombination occurs in the surface states related to N-Si-O bonds.
    Preview · Article · Apr 2014 · Optical Materials Express
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    ABSTRACT: Strong tunable photoluminescence (PL) from silicon oxynitride materials have been demonstrated by modulating the oxygen content. The increase of oxygen content in the films from 8% to 61% results in red, orange-yellow and white switching PL. The change in PL characteristics of these films is ascribed to the variation of defect luminescent centers as well as the evolution of dominant phase structures changing from silicon nitride to silicon oxynitride and silicon oxide. The intense PL intensity is suggested from the nanoseconds recombination lifetime as well as the alleviation of internal stress in silicon oxynitride.
    Preview · Article · Feb 2014 · Optical Materials Express
  • Chao Song · Xiang Wang · Rui Huang · Jie Song · Yanqing Guo
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    ABSTRACT: Boron doped hydrogenated amorphous silicon thin films were prepared by plasma-enhanced chemical vapor deposition technique at various flow rate of diborane (F-B). As-deposited samples were thermally annealed at the temperature of 800 degrees C to obtain the doped nanocrystalline silicon (nc-Si) films. The effect of boron concentration on the microstructural, optical and electrical properties of the films was investigated. X-ray photoelectron spectroscopy (XPS) measurements demonstrated the presence of the substitutional boron in the doped films. It was found that thermal annealing can efficiently activate the dopants in films accompanying with formation of nc-Si grains. Based on the temperature-dependent conductivity measurements, it was shown that the dark conductivity of doped amorphous samples increases monotonously with the increase of doping content. While the dark conductivity of doped nc-Si films is not only determined by the concentration of dopant but also the crystallinity of the films. As increasing the flow rate of diborane, the crystallinity of doped nc-Si films decreases, which causes the decrease of dark conductivity. Finally, the high dark conductivity of 178.68 S cm(-1) of the B-doped nc-Si thin films can be obtained.
    No preview · Article · Oct 2013 · Materials Chemistry and Physics
  • Chao Song · Cong Li · Jun Xu · Rui Huang · Xiang Wang · Jie Song · Yan Qing Guo
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    ABSTRACT: The effects of laser fluence on the microstructure and electrical properties of nanocrystalline silicon films were investigated on samples prepared by a plasma-enhanced chemical vapor deposition technique. It was found that the content of hydrogen in the films could be reduced gradually by increasing the laser fluence, accompanied by the formation of nc-Si. The evolution of hydrogen is responsible for a change in the optical band gap and dark conductivity. By controlling the laser fluence at 1.0 J cm−2, a dark conductivity as high as 5.9 × 10−3 S cm−1 could be obtained. Based on measurements of the temperature-dependent conductivity, the carrier transport processes are discussed. The effusion of hydrogen and the increase of crystallinity are thought to be contributed to the high dark conductivity and low conductivity activation energy.
    No preview · Article · May 2013 · Laser Physics
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    ABSTRACT: Embryonic stem cells (ESCs) may be useful as a therapeutic source of cells for the production of healthy tissue; however, they are associated with certain challenges including immunorejection as well as ethical issues. Induced pluripotent stem cells (iPSCs) are a promising substitute since a patient's own adult cells would serve as tissue precursors. Ethical concerns prevent a full evaluation of the developmental potency of human ESCs and iPSCs, therefore, mouse iPSC models are required for protocol development and safety assessments. We used a modified culturing protocol to differentiate pluripotent cells from a mouse iPS cell line and two mouse ES cell lines into neurons. Our results indicated that all three pluripotent stem cell lines underwent nearly the same differentiation process when induced to form neurons in vitro. Genomic expression microarray profiling and single-cell RT-qPCR were used to analyze the neural lineage differentiation process, and more than one thousand differentially expressed genes involved in multiple molecular processes relevant to neural development were identified.
    Preview · Article · May 2013 · International Journal of Molecular Medicine
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    Chao Song · Rui Huang · Xiang Wang · Yanqing Guo · Jie Song
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    ABSTRACT: A tunable red photoluminescence from a-Si:H/a-SiNx multilayers was modulated in the wavelength range of 800–640 nm by controlling the thickness of the a-Si:H sublayer from 4 to 1.5 nm. Subsequent annealing was used to improve red photoluminescence without recrystallization of the amorphous silicon sublayers. The significant enhancement of red emission was found to depend on the decomposition of the Si–H bond in a-Si:H sublayers. Based on the absorption measurement, Raman, and FTIR spectra, the origin of light emission is ascribed to the silicon dangling bonds associated with hydrogen in a-Si:H sublayers, and the mechanism of light emission is suggested from the radiative recombination between the electrons existing at the negatively charged levels of silicon dangling bond and holes at the valence band.
    Preview · Article · May 2013 · Optical Materials Express
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    ABSTRACT: We report a remarkable improvement of photoluminescence from ZnO-core/a-SiN<sub>x</sub>:H-shell nanorod arrays by modulating the bandgap of a-SiN<sub>x</sub>:H shell. The a-SiN<sub>x</sub>:H shell with a large bandgap can significantly enhance UV emission by more than 8 times compared with the uncoated ZnO nanorods. Moreover, it is found that the deep-level defect emission can be almost completely suppressed for all the core-shell nanostructures, which is independent of the bandgaps of a-SiN<sub>x</sub>:H shells. Combining with the analysis of infrared absorption spectrum and luminescence characteristics of NH<sub>3</sub>-plasma treated ZnO nanorods, the improved photoluminescence is attributed to the decrease of nonradiative recombination probability and the reduction of surface band bending of ZnO cores due to the H and N passivation and the screening effect from the a-SiN<sub>x</sub>:H shells. Our findings open up new possibilities for fabricating stable and efficient UV-only emitting devices.
    No preview · Article · Mar 2013 · Optics Express
  • Xiang Wang · Rui Huang · Chao Song · Yanqing Guo · Jie Song
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    ABSTRACT: We report the effect of barrier layer on the electroluminescence from Si/SiOxNy multilayer structures, where the SiOxNy barrier layers were modulated by varying the oxygen/nitride ratio. It is found that the electroluminescence efficiency is significantly enhanced by more than one order of magnitude through controlling the oxygen/nitride ratio. The high emission efficiency is ascribed to the equivalent carrier injections that increase the carrier recombination probability. In addition, the strong confinement of carriers as a result of the increase of the barrier height also plays a role in the increasing radiative recombination efficiency.
    No preview · Article · Feb 2013 · Applied Physics Letters
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    ABSTRACT: Aim: To investigate the effects of advanced glycation end products (AGEs) on calcification in human aortic smooth muscle cells (HASMCs) in vitro and the underlying mechanisms. Methods: AGEs were artificially prepared. Calcification of HASMCs was induced by adding inorganic phosphate (Pi, 2 mmol/L) in the media, and observed with Alizarin red staining. The calcium content in the supernatant was measured using QuantiChrome Calcium Assay Kit. Expression of the related mRNAs and proteins was analyzed using real-time PCR and Western blot, respectively. Chromatin immunoprecipitation (ChIP) assay was used to detect the binding of NF-κB to the putative IGF1R promoter. Results: AGEs (100 μg/mL) significantly enhanced Pi-induced calcification and the levels of osteocalcin and Cbfα1 in HASMCs. Furthermore, the treatment decreased the expression of insulin-like growth factor 1 receptor (IGF1R). Over-expression of IGF1R in HASMCs suppressed the AGEs-induced increase in calcium deposition. When IGF1R expression was knocked down in HASMCs, AGEs did not enhance the calcium deposition. Meanwhile, AGEs time-dependently decreased the amounts of IκBα and Flag-tagged p65 in the cytoplasmic extracts, and increased the amount of nuclear p65 in HASMCs. In the presence of NF-κB inhibitor PDTC (50 μmol/L), the AGEs-induced increase in calcium deposition was blocked. Over-expression of p65 significantly enhanced Pi-induced mineralization, but suppressed IGF1R mRNA level. Knockdown of p65 suppressed the AGEs-induced increase in calcium deposition, and rescued the IGF1R expression. The ChIP analysis revealed that NF-κB bound the putative IGF1R promoter at position −230 to −219 bp. The inhibition of IGF1R by NF-κB was abolished when IGF1R reporter plasmid contained mutated binding sequence for NF-κB or an NF-κB reporter vector. Conclusion: The results demonstrate that AGEs promote calcification of human aortic smooth muscle cells in vitro via activation of NF-κB and down-regulation of IGF1R expression.
    Preview · Article · Feb 2013 · Acta Pharmacologica Sinica
  • Xiang Wang · Chao Song · Yanqing Guo · Jie Song · Rui Huang

    No preview · Article · Jan 2013 · Modeling and Numerical Simulation of Material Science
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    ABSTRACT: Luminescent amorphous silicon nitride films were prepared with different hydrogen flow rates in very high frequency plasma enhanced chemical vapor deposition system. Very bright orange-red light emissions can be clearly observed with the naked eye in a bright room for the films grown at the hydrogen flow rate of 30 sccm. The photoluminescence intensity of the film grown at the hydrogen flow rate of 30 sccm is found to be four times higher than that of the film without hydrogen dilution. However, with further increasing the hydrogen flow rate from 30 to 90 sccm, the photoluminescence intensity of the film rapidly decreases. Fourier-transform infrared absorption spectra indicate that the introduction of N-H bonds is of a key role to enhance the photoluminescence intensity of the films. Based on the measurements of structural and bonding configurations, the improved photoluminescence intensity is attributed to the well hydrogen passivation of nonradiative defect states related to N at proper hydrogen flow rates.
    Preview · Article · Dec 2012 · Physics Procedia
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    ABSTRACT: Human induced pluripotent stem (iPS) cells have the ability to differentiate into all somatic cells and to maintain unlimited self-renewal. Therefore, they have great potential in both basic research and clinical therapy for many diseases. To identify potentially universal mechanisms of human somatic cell reprogramming, we studied gene expression changes in three types of cells undergoing reprogramming. The set of 570 genes commonly regulated during induction of iPS cells includes known embryonic stem (ES) cell markers and pluripotency related genes. We also identified novel genes and biological categories which may be related to somatic cell reprogramming. For example, some of the down-regulated genes are predicted targets of the pluripotency microRNA cluster miR302/367, and the proteins from these putative target genes interact with the stem cell pluripotency factor POU5F1 according to our network analysis. Our results identified candidate gene sets to guide research on the mechanisms operating during somatic cell reprogramming.
    No preview · Article · Dec 2012 · Journal of Genetics and Genomics
  • Xiang Wang · Song Chao · Yan Qing Guo · Jie Song · Rui Huang
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    ABSTRACT: Stack nanocrystalline-Si (nc-Si) based metal insulator semiconductor memory structure was fabricated by plasma enhanced chemical vapor deposition. The doubly stacked layers of nc-Si with the thickness of about 5 nm were fabricated by the layer-by-layer deposition technique with silane and hydrogen mixture gas. Capacitance-Voltage (C-V) measurements were used to investigate electron tunnel and storage characteristic. Abnormal capacitance hysteresis phenomena are obtained. The C-V results show that the flatband voltage increases at first, then decreases and finally increases, exhibiting a clear deep at gate voltage of 9 V. The charge transfer effect model was put forward to explain the electron storage and discharging mechanism of the stacked nc-Si based memory structure. The decreasing of flatband voltage at moderate programming bias is attributed to the transfer of electrons from the lower nc-Si layer to the upper nc-Si layer.
    No preview · Article · Dec 2012 · Key Engineering Materials
  • Rui Huang · Jie Song · Yan Qing Guo · Chao Song · Xiang Wang
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    ABSTRACT: The N-rich a-SiNx:H films were deposited on Si substrates by very high frequency plasma enhanced chemical vapor deposition technique at a low temperature of 250 °C. Strong blue photoluminescence (PL), which originates from nitrogen dangling bond, can be observed in the as-deposited samples. The dependence of defect PL on annealing temperature was systematically investigated. The PL spectra reveal that the PL peak is almost independent of the annealing temperatures while the luminescence intensity rapidly decreases with the annealing temperature increasing from 400°C to 600°C. However, higher annealing temperatures over 700 °C results in an enhancement of luminescence intensity. Based on the relationship between PL spectra and bonding configurations of the samples, the evolution of defect PL with annealing temperatures was briefly discussed.
    No preview · Article · Dec 2012 · Key Engineering Materials
  • Yan Qing Guo · Xiang Wang · Chao Song · Rui Huang · Jie Song
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    ABSTRACT: In recent years, hydrogenated nanocrystalline silicon (nc-Si:H) film has received much attention due to its potential application in various optoelectronic devices. In the present work, nanocrystalline silicon (nc-Si) films were fabricated from SiH4 diluted with H2 in very high frequency (40.68 MHz) plasma enhanced chemical vapor deposition system. The influence of radio frequency (rf) power on the structural properties of nanocrystalline silicon films has been studied. Raman spectra show that the crystallinity of the nc-Si films can be increased by promoting the rf power. But over high rf power leads to the structural deterioration of nc-Si:H film. AFM images manifest that, with the increase of deposition time, the grain size becomes larger accompanied by the decrease of the number density.
    No preview · Article · Dec 2012 · Key Engineering Materials

Publication Stats

325 Citations
109.61 Total Impact Points


  • 2010-2015
    • Hanshan Normal University
      Ch’ao-chou-chen, Guangdong, China
  • 2009-2013
    • Shanghai Jiao Tong University
      • • School of Medicine
      • • Institute of Medical Genetics
      • • Department of Pediatric Surgery
      Shanghai, Shanghai Shi, China
  • 2011
    • Beijing Jiaotong University
      Peping, Beijing, China
  • 2007-2009
    • Nanjing University
      • Department of Physics
      Nan-ching, Jiangsu Sheng, China