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  • Structural characterization of TiO 2 thin films prepared by pulsed laser deposition on GaAs(1 0 0) substrates

    • 摘要:

      TiO 2 thin films on GaAs(1 0 0) substrates were prepared at temperature ranging 30-750°C and pressure from 5 × 10 -4 Pa base vacuum to 15 Pa O 2 , by pulsed laser deposition (PLD). The effects of both the oxygen pressure and the substrate temperature on the properties of TiO 2 films were investigated. TiO 2 thin films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). Optimum parameters have been identified for the growth of high-quality TiO 2 films. At 5 Pa of oxygen ambient pressure, rutile TiO 2 films with high [1 1 0] orientation were formed at substrate temperature of 700°C. At room temperature (30°C) and 5 × 10 -4 Pa base vacuum, rutile TiO 2 films with a preferred [1 1 0] orientation were also obtained on GaAs(1 0 0) substrates by PLD. Surface morphology of the films showed marked dependence on the substrate temperature. The grain size and their surface roughness increased with raising substrate temperature. © 2001 Elsevier Science B.V.

    • 作者:

      Liu Xiaohua;Yin J.;Liu Z. G.;Yin X. B.;Chen G. X.;Wang M.

    • 刊名:

      Applied Surface Science

    • 在线出版时间:

      2001

  • H3O+-dependent morphological change in the electrochemical deposition of iron

    • 摘要:

      By in situ optical microscopy and scanning electron microscopy, we investigate the morphology of the iron electrodeposit grown at different H3O+ concentration in the electrolyte. The chemical composition of the electrodeposit is analyzed by X-ray diffraction and Mössbauer spectroscopy. It seems that the morphological transitions observed in this system do not relate to the oxidation/passivation of the metallic deposit during the growth. The possible origin of the dependence of deposit morphology on the H3O+ in the electrolyte is discussed. © 2001 Elsevier Science B.V.

    • 作者:

      Zhang Ke-Qin;Wang Mu;Peng Ru-Wen;Xiao Yuming;Ming Nai-ben

    • 刊名:

      Physics Letters Section A General Atomic and Solid State Physics

    • 在线出版时间:

      2001

  • Modification of a YBa2Cu3O7-δ thin film using an atomic force microscope

    • 摘要:

      A YBa2Cu3O7-δ thin film is modified by a probe electric field of an atomic force microscope to form a ridge with the width of only a grain cell. The modification varies with the operation parameters of the bias voltage, the moving velocity of the probe and the ambient humidity. Energy dispersive spectroscopy analysis shows only oxygen deficiency in the modified YBCO thin film. As a result, the suppressed superconductivity was found in the junction crossing the ridge.

    • 作者:

      You Li-Xing;Feng Yi-Jun;Yang Sen-Zu;Kang Lin;Wang Mu;Wu Pei-Heng;Yin Xiao-Bo

    • 刊名:

      Chinese Physics Letters

    • 在线出版时间:

      2002

  • Different growth behavior of SrBi2Ta2O9 ferroelectric films under conventional and rapid annealing processing by metalorganic decomposition

    • 摘要:

      SrBi2Ta2O9 (SBT) thin films were prepared on Pt/TiO2/SiO2/Si substrates by metalorganic decomposition method. The grain growth behaviors of SBT films under conventional furnace annealing (CFA) and rapid thermal annealing (RTA) processing as functions of annealing temperature (T) and time (t) were investigated systematically. The grain size distribution with CFA and RTA basically conforms to Gaussian distribution, whereas the films annealed by RTA show higher nucleation rate than by CFA. Different grain growth kinetics of the films annealed at 750°C under CFA and RTA with varied anneal time was characterized. In Arrhenius curves, there were two distinct temperature regions corresponding to different growth activation energies. The value of growth activation energy under CFA is smaller than that under RTA. © 2002 Elsevier Science B.V. All rights reserved.

    • 作者:

      Li Ai-Dong;Wu Di;Ling Hui-Qin;Wang Mu;Liu Zhiguo;Ming Naiben

    • 刊名:

      Journal of Crystal Growth

    • 在线出版时间:

      2002

  • Persistent currents in k-component fibonacci mesoscopic rings threaded by a magnetic flux

    • 摘要:

      On the basis of the tight-binding model, we have studied the energy spectra and persistent currents (PCs) in one-dimensional k-component Fibonacci (KCF) mesoscopic rings threaded by a magnetic flux. The KCF structures, which contain k basic units, can be periodic (if k = 1), quasiperiodic (if 1 < k < 6), and intermediate cases between quasiperiodicity and disorder (if k ≥ 6). It is shown that the flux-dependent eigenenergies form 'band' structure in the KCF rings. The subbands possess the hierarchical characteristic with self-similarity if 1 < k < 6, while if k ≥ 6, there is no obvious self-similarity in the subbands. In fact, the energy spectra ultimately determine the behaviour of the PCs in the mesoscopic KCF rings. On one hand, the PC depends on the total energy bandwidth: the narrower the bandwidth, the smaller the PC. On the other hand, the parity effect of electrons is dissimilar in different KCF rings. As k increases, there is less likelihood of observing a dramatic change in currents of several orders of magnitude when one electron is added to or removed from the KCF rings. If k is large enough, the current behaviour may approach some features of disordered systems.

    • 作者:

      Liu Y. M.;Peng R. W.;Jin G. J.;Huang X. Q.;Wang M.;Hu. A.;Jiang S. S.

    • 刊名:

      Journal of Physics Condensed Matter

    • 在线出版时间:

      2002

  • Absence of suppression in the persistent current by delocalization in random-dimer mesoscopic rings

    • 摘要:

      We study the persistent current (PC) in one-dimensional (ID) magnetic-flux threaded mesoscopic rings, which is constructed according to the random-dimer (RD) model. It is found that the PC varies significantly when the Fermi energy is changed in the system. The PC can approach the behaviour of free electrons regardless of the disorder if there is the extended electronic state at the Fermi level; while the PC can be depressed dramatically if the highest-occupied electronic state is localized or in the intermediate case between the extended state and localized one. This property provides a possible explanation to the anomalously large PC observed in some experiments. Furthermore, it is demonstrated that the electronic delocalization leads to unsuppressed persistent currents and √N unscattered states exist around the resonant energy in the RD model from the viewpoint of the PC. The possibility to use ID random-dimer mesoscopic rings as quantum-switch devices is also discussed. © 2003 The Physical Society of Japan.

    • 作者:

      Liu Y. M.;Peng R. W.;Huang X. Q.;Wang Mu;Hu A.;Jiang S. S.

    • 刊名:

      Journal of the Physical Society of Japan

    • 在线出版时间:

      2003

  • Growth and characterization of Al 2 O 3 gate dielectric films by low-pressure metalorganic chemical vapor deposition

    • 摘要:

      Ultrathin Al 2 O 3 films have been deposited on n-Si substrates by low-pressure metalorganic chemical vapor deposition (MOCVD) as gate dielectrics for next generation MOSFET applications. Al(acac) 3 was used as metalorganic precursor. Impacts of substrate temperature and post-annealing in O 2 or N 2 on equivalent oxide thickness (EOT), leakage current density (J A ) and carbon residue of Al 2 O 3 films have been studied. It is found that post-annealing is necessary for ultrathin Al 2 O 3 films to obtain good electrical properties. The EOT shows slight deposition temperature dependence and the lowest EOT value with ∼0.8 nm is obtained at 600°C. Typical Al 2 O 3 ultrathin films have larger frequency dependence and EOT of ∼1.2 nm with J A of 36 mA/cm 2 at V g =+1 V. AES depth profiles demonstrate that post-annealing in an O 2 atmosphere could effectively eliminate the carbon contamination of Al 2 O 3 films. Meanwhile, further post-annealing in N 2 could decrease the J A of Al 2 O 3 films to 8 mA/cm 2 . © 2002 Elsevier Science B.V. All rights reserved.

    • 作者:

      Shao Qi-Yue;Li Ai-Dong;Ling Hui-Qin;Wu Di;Wang Yuan;Feng Yan;Liu Zhi-Guo;Wang Mu;Ming Nai-Ben;Yang Sen-Zu

    • 刊名:

      Microelectronic Engineering

    • 在线出版时间:

      2003

  • Spontaneous correlation of crystallographic orientations in crystallite aggregation: Physical origin and its influence on pattern formation

    • 摘要:

      In our previous work we demonstrated an unusual crystallite aggregate in which the crystallites correlate in crystallographic orientation and form a fractal pattern with strong anisotropy (Wang, M.; et al. Phys. Rev. Lett. 1998, 80, 3089. Liu, X. Y.; et al. J. Cryst. Growth 2000, 208, 687.). Yet it remains unanswered why each crystallite appears with specific orientation and obeys a strict order. Here we report an in-depth study of the origin of the long-range correlation of the crystallographic orientations in the aggregate investigated by means of micro-X-ray-diffraction, atomic force microscopy, and in-situ optical observation. The experimental data suggest that the topographic regularity of the aggregate arises from the consecutive rotation of the crystallographic orientation in the nucleation-mediated growth. This effect may occur when nucleation takes place in a region with inhomogeneous surface tension, and may help us to understand the long-range ordering effect in aggregating crystallites.

    • 作者:

      Li Da-Wei;Wang Mu;Peng Ru-Wen;Ming Nai-Ben;Liu Peng

    • 刊名:

      Journal of Physical Chemistry B

    • 在线出版时间:

      2003

  • Pulsed laser deposition of YBa2Cu3O 7-δ/I/LaNiO3trilayers (I = SrTiO3, CeO2 or Eu2CuO4 on (100) SrTiO3 substrates

    • 摘要:

      To look at a quasi-particle injection into high Tc superconductors, YBa2Cu3O 7-δ/insulator/LaNiO3 (YBCO/I/LNO) trilayers have been grown on (100) SrTiO3 substrates in situ by pulsed laser deposition (PLD), where, an insulator (I), SrTiO3 (STO), CeO 2 (CO) or Eu2CuO4 (ECO) are used. All the deposited films are highly oriented. The surface morphology of LNO and the insulating films is investigated during fabrications after the films are made, revealing small roughness and low droplet density. The top YBCO layer exhibits good superconducting properties with a critical temperature above 82 K and a transition width as sharp as 1.5 K.

    • 作者:

      Sun G. Z.;Wu P. H.;Fan S. X.;Ji Z. M.;Yang S. Z.;Xu W. W.;Rang L.;Feng Y.;Wang M.

    • 刊名:

      Superconductor Science and Technology

    • 在线出版时间:

      2003

  • Resonant transmission and frequency trifurcation of light waves in Thue-Morse dielectric multilayers

    • 摘要:

      We present in this letter the observation of the optical resonant transmission of Thue-Morse (TM) dielectric multilayers. For the first time the frequency trifurcation feature has been experimentally demonstrated. This effect can be analogous to the electronic energy spectrum of a TM system, which has not yet been directly obtained in experiments. The resonant transmission originates from the positional correlation of the basic units in the TM system, and is sensitive to the modulation of optical thickness. The experimental results are in good agreement with the theoretical analysis.

    • 作者:

      Qiu F.;Peng R. W.;Huang X. Q.;Liu Y. M.;Wang M.;Hu A.;Jiang S. S.

    • 刊名:

      Europhysics Letters

    • 在线出版时间:

      2003

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