Y. Cao
Chinese Academy of Sciences
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Featured researches published by Y. Cao.
Journal of Crystal Growth | 2000
Junbao Li; X.L Chen; Zhiyu Qiao; Y. Cao; Y.C. Lan
Abstract GaN nanorods with diameters of 10–45xa0nm were formed through a simple sublimation method. They were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). SEM images showed that the nanorods were straight. XRD, SAED and HRTEM indicated that the nanorods were wurtzite GaN single crystals.
Journal of Crystal Growth | 1999
Y.C. Lan; X. L. Chen; Y. Cao; Y.P. Xu; L.D Xun; T. Xu; J. K. Liang
High-quality aluminum nitride powder was obtained through the reaction of aluminum metal with ammonia at 450 degrees C in an autoclave. The synthesized powder was characterized by X-ray powder diffraction, high-resolution transmission electron microscopy (HRTEM) and photoluminescence spectrum. X-ray diffraction and HRTEM indicated that the powder consisted of wurtzite AIN with an average size of about 32 nm. Photoluminescence spectrum confirmed the existence of a blue luminescence band in AIN due to nitrogen vacancies. A possible low-temperature synthesis mechanism was discussed
Journal of Crystal Growth | 2000
Y. Cao; X.L Chen; Y.C. Lan; Junliang Li; Yingqiang Xu; T. Xu; Quanlin Liu; J. K. Liang
Photoluminescence and Raman scattering spectra from AIN nanocrystalline powders are studied. A blue emission band centered at 420 nm (2.95 eV) is observed. This band may be ascribed to the transition from the shallow level of V-N to the ground state of the deep level of the V-Al(3-)-3 x O-N(+) defect complexes. A phonon structure resulting fi om the transition from the shallow level to the excited states of the deep level is also observed. The broadening of peaks and the low-wave-number-shift of the phonon frequency observed on the Raman scattering spectra are the result of nano-sized effects
Materials Research Bulletin | 2000
Y.C. Lan; X.L Chen; Yantao Xu; Y. Cao; Feifei Huang
A double layer CeO2/Nb2O5 thin film by magnetron sputtering was prepared. The property and microstructure of the thin film were carefully characterized by x-ray photoelectron spectroscopy (XPS), transmission electron microscopy, and high resolution transmission electron microscopy, XPS measurement clearly demonstrated that the Nb2O5 layer underlying CeO2 as a electrical-conductive layer could greatly improve the reduction ability of CeO2 thin film compared with that of a single layer CeO2 thin film: Fitting to the XPS experimental data and deconvoluting the spectra showed the increase of Ce3+ concentration in the double layer CeO2/Nb2O5 thin film. The microstructure of the double layer thin film was composed of three distinguishable layers, which are a polycrystalline CeO2 layer, an amorphous Nb2O5 layer, and an intermediate amorphous layer with regard to the silicon substrate. The interface between CeO2 and Nb2O5 was rough and indistinct. A detailed analysis was given from the viewpoint of interdiffusion at the CeO2/Nb2O5 interface
Journal of Alloys and Compounds | 2000
Junliang Li; Zhiyu Qiao; X. L. Chen; Lian Chen; Y. Cao; Ming-Xia He; H. Li; Zhiqin Cao; Z.F. Zhang
Abstract β-Ga 2 O 3 nanorods with diameters of 10–60 nm were synthesized through a simple gas reaction method and were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). The SEM image showed that most of the nanorods were straight. XRD, SAED and HRTEM indicated that the nanorods were monoclinic Ga 2 O 3 single crystals.
Journal of Crystal Growth | 2001
X. L. Chen; Y.C. Lan; Junliang Li; Y. Cao; Meng He
In this brief paper, wt: address the problem of the radial growth dynamics of a nanowire due to the vapor-solid (VS) process while at the same time it grows along its axial direction due to vapor-liquid-solid (VLS) process. We show that there exists a critical radius at a certain saturation and that the nanowire will thicken if its initial radius is larger than the critical radius and vice versa. Only when its initial radius is equal to the critical radius will the radius of the nanowire be uniform along its axial direction. In all other cases, the nanowire is tapered with a certain slope. The slope is relevant to the initial radius. The closer it is to the critical radius, the smaller is the slope and vice versa. Although the slope may be generally very small, it still does exist. This suggests that it is difficult to grow long nanowires with a uniform radius
Journal of Alloys and Compounds | 2001
Y. Zhang; X. L. Chen; J. K. Liang; Y. Cao; T. Xu
The subsolidus phase relations of the system La2O3-CaO-B2O3 are investigated by means of X-ray diffraction (XRD) analyses. There are seven binary compounds and five ternary compounds in this system. The phase diagram comprises eighteen three-phase regions. A new ternary compound Ca4LaO(BO3)(3) (CLOB) is identified. It has a monoclinic structure with cell parameters a=8.1732(1) Angstrom, b=16.0860(3) Angstrom, c=3.6268(1) Angstrom, beta =101.40(1)degrees and space group Cm. At low temperature, the XRD patterns of the CLOB compound indicate that a phase transition in the low temperature range is absent. The expansion coefficients in the three major directions are different, the value of alpha (c) being the largest
Journal of Crystal Growth | 2002
Y. Cao; Huanchu Chen; Jing-Bo Li; Changcun Ge; S.Y. Tang; J.X. Tang; X. L. Chen
alpha -Si3N4 whiskers with diameters of about 0.1 mum and length of 3-5 mum were fabricated through combustion synthesis route under very low nitrogen pressure of 0.5-1 MPa. The measured maximum combustion temperature is about 1863 K which is rather lower than the adiabatic temperature (about 4400 K) and the decomposition temperature (about 2170 K) of Si3N4 under atmospheric pressure. The addition of NaN3 catalyst plays a key role in the formation of alpha -Si3N4 whiskers under such low nitrogen pressure
Journal of Crystal Growth | 2000
X.L Chen; Y. Cao; Y.C. Lan; Xiaoqing Xu; J. Q. Li; Kunquan Lu; P.Z. Jiang; T. Xu; Z. G. Bai; Yunlong Yu; Jiben Liang
A new condensed form of GaN, nanocrystal-assembled bulk (NAB) GaN, was obtained directly from reactions of metal Ga and NH4Cl in liquid ammonia at 350-500 degrees C. High-resolution transmission electron microscopy observations reveal that the NAB GaN consists of well-crystallized nanocrystals with wurtzite structure. The synchronous densificated NAB GaN is transparent to visible light while the constituted nanocrystals have an average size of about 12 nm. A possible synthesis mechanism is discussed
Review of Scientific Instruments | 2006
H. W. Zhao; L. T. Sun; X. Z. Zhang; Z. M. Zhang; X. H. Guo; W. He; P. Yuan; Mingtao Song; J. Y. Li; Y. C. Feng; Y. Cao; X. X. Li; W.L. Zhan; B. Wei; D. Z. Xie
Superconducting electron cyclotron resonance (ECR) ion source with advanced design in Lanzhou (SECRAL) is a next generation ECR ion source and aims for developing a very compact superconducting ECR ion source with a structure and high performances for highly charged ion-beam production. The ion source was designed to be operated at 18GHz at initial operation and finally will be extended to 28GHz. The superconducting magnet confinement configuration of the ion source consists of three axial solenoid coils and six sextupole coils with a cold iron structure as field booster and clamping. At full excitation, this magnet assembly can produce peak mirror fields on the axis of 3.6T at injection, 2.2T at extraction, and a radial sextupole field of 2.0T at plasma chamber wall. What is different from the traditional design, such as LBNL VENUS and LNS SERSE, is that the three axial solenoid coils are located inside of the sextupole bore in order to reduce the interaction forces between the sextupole coils and the so...