Zhenqiang Xi

Zhejiang University of Science and Technology, Hang-hsien, Zhejiang Sheng, China

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Publications (29)44.54 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: n-Type cuprous oxide was synthesized by controlling the bath pH of the electro-deposition. Thereafter, cuprous oxide films were annealed in nitrogen at different temperatures. The electrical properties of n-type cuprous oxide films before and after annealing were studied by the capacitance–voltage measurements. By analysis of the Mott–Schottky curves, it was found that the carrier concentration of cuprous oxide films varied with the deposition bath pH and the annealing temperature. Also, the flat-band potential shifted with the increasing annealing temperature.
    Thin Solid Films 01/2012; 520(7):2708–2710. · 1.87 Impact Factor
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    ABSTRACT: Tb(3+)-doped Gd(2)O(3) (Gd(2)O(3):Tb(3+)) nanofibers were prepared via a simple electrospinning technique using poly(ethylene oxide) (PEO) and rare-earth acetate tetrahydrates (Ln(CH(3)COO)(3)·4H(2)O (Ln = Gd, Tb)) as precursors. The obtained nanofibers have an average diameter of about 80 nm and are composed of pure cubic Gd(2)O(3) phase. A possible formation mechanism for the nanofibers is proposed on the basis of the experimental results, which reveals that PEO acts as the structure directing template during the whole electrospinning and subsequent calcination process. The luminescent properties of the nanofibers were investigated in detail. The nanofibers exhibit a favorable fluorescent property symbolized by the characteristic green emission (545 nm) resulting from the 5D4-->7F5 transition of Tb(3+). Concentration quenching occurs when the Tb(3+) concentration is 3 at.%, indicating that the Gd(2)O(3):Tb(3+) nanofibers have an optimum luminescent intensity under such a doping concentration.
    Nanotechnology 01/2011; 22(3):035602. · 3.84 Impact Factor
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    ABSTRACT: In this work, two Tb3+ activated green phosphors: Y2O3:Tb3+ and YBO3:Tb3+ were prepared by hydrothermal method. Photoluminescence properties of both phosphors were studied in details. Both phosphors exhibit similar luminescent characteristics symbolized by the dominant green emission at 545 nm. Concentration quenching occurs at the Tb3+ concentration of 1.60 atomic% and 2.57 atomic% for Y2O3:Tb3+ and YBO3:Tb3+, respectively. Luminescence decay properties were characterized to better understand the mechanism of concentration quenching. Based on the calculation, the concentration quenching in both phosphors was caused by the dipole–dipole interaction between Tb3+ ions.
    Materials Chemistry and Physics. 02/2010; 119(3):490–494.
  • Electrochemical and Solid State Letters - ELECTROCHEM SOLID STATE LETT. 01/2010; 13(6).
  • Electrochemical and Solid State Letters - ELECTROCHEM SOLID STATE LETT. 01/2010; 13(6).
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    ABSTRACT: Y2O3:Eu3+ red-emitting thin film phosphor was prepared by a two-step process: the cathodical deposition of thin film of yttrium hydroxide and europium hydroxide followed by an annealing process to achieve Eu3+ doped Y2O3 film. It is found that the atomic content of Eu3+ can be well controlled by simply adjusting the volume ratio of Y(NO3)3 to Eu(NO3)3 solutions. Dependence of the photoluminescence intensity on the atomic content of Eu3+ in Y2O3 was also studied. The best photoluminescence performance of Y2O3:Eu3+ thin film phosphor was achieved as atomic content of Eu3+ equal to 1.85at.%.
    Thin Solid Films 01/2010; 518(17):4817-4820. · 1.87 Impact Factor
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    ABSTRACT: Non-crystalline copper indium disulphide (CuInS2) thin films had been deposited on ITO glass by chemical bath deposition (CBD) in acid conditions. Then polycrystalline CuInS2 films were obtained after sulfuration in sulfur atmosphere at 450 °C for 1.5 h. The films had been characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), Raman scattering measurements and energy dispersive X-ray analysis (EDX). The optical and electrical property of the thin films was also measured. The results showed that the pure, flatness, and well crystallized CuInS2 thin films with good electrical and optical property had been obtained, meaning that the chemical bath deposition in acid conditions is suitable for the deposition of CuInS2 thin films.
    Journal of Materials Science Materials in Electronics 01/2009; 20(7):609-613. · 1.49 Impact Factor
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    ABSTRACT: The iron precipitation in as-received Czochralski (CZ) silicon during low temperature from 300 to 700 °C was investigated. It was found that the iron precipitation rate was increased in turn from 300 to 700 °C. It was also found that the iron could form small precipitates even at low concentration. Moreover, iron precipitation was revealed as the diffusion-limited process, which could be described properly by Ham's law. This performance of iron precipitation in as-received CZ silicon was considered to be significantly influenced by the grown-in oxygen precipitates because of the fact that the grown-in oxygen precipitates could act as the heterogeneous nuclei for interstitial iron.
    Materials Science in Semiconductor Processing. 01/2009;
  • Electrochemical and Solid State Letters - ELECTROCHEM SOLID STATE LETT. 01/2009; 12(8).
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    ABSTRACT: A general hydrothermal process with use of lanthanide (III) nitrates and Na2SnO3 as precursors has been proposed for synthesizing nanocrystalline lanthanide stannates with general formula: Ln2Sn2O7 (Ln=Y, La–Yb). Stannates of all lanthanides except for the radioactive promethium were successfully synthesized. Characterization by XRD and TEM revealed that all the products were phase-pure nanocrystalline lanthanide stannates with pyrochlore-type structure. Photoluminescent properties of three samples (i.e. Tb2Sn2O7, Dy2Sn2O7 and Yb2Sn2O7) are also presented. The mole ratio of Ln(NO3)3:Na2SnO3 and hydrothermal temperature were two key factors for this general hydrothermal route.
    Journal of Alloys and Compounds 01/2008; 464(1):508-513. · 2.73 Impact Factor
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2008; 39(51).
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    ABSTRACT: This work focuses on the synthesis of tetragonal zirconia (ZrO2) nanocrystallites with diameters of 5 nm by a simple hydrothermal process in the presence of hydrazine hydrate. Structural characterization of the ZrO2 products using X-ray diffraction and Raman spectroscopy revealed that the predominant crystal phase was the tetragonal phase. High-resolution transmission electron microscopy images further showed that that the diameter of the majority of the tetragonal ZrO2 nanocrystallites was <5 nm. Furthermore, we discussed the mechanism of the hydrothermal process and the critical roles of hydrazine hydrate in the hydrothermal formation of the small-sized ZrO2 nanocrystallites.
    Journal of the American Ceramic Society 03/2007; 90(4):1334 - 1338. · 2.43 Impact Factor
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    ABSTRACT: A model, including segregation from silicon melt to silicon crystal as well as evaporation from silicon melt to Ar atmosphere, was established for simulating the oxygen distribution in multicrystalline silicon (mc-si) ingot, which shows good agreement with the experimental results. According to this model, the oxygen distribution in the bottom of ingot is mainly determined by the evaporation of oxygen, whereas that in the top of ingot is dominated by the segregation of oxygen. Furthermore, it could be found that the Oi profiles in growth direction of ingots become more and more steeper with the increase of the exponent X.
    Solar Energy Materials and Solar Cells 01/2007; 91(18):1688-1691. · 5.03 Impact Factor
  • Guoyin Huang, Zhenqiang Xi, Deren Yang
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    ABSTRACT: In the present work, the effect of low temperature short-time rapid thermal processing (RTP) pretreatment on the average grain size and the crystallinity of the polycrystalline silicon thin films, fabricated by subsequent solid phase crystallization (SPC) of amorphous silicon (a-Si) thin films grown by radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) at high temperature has been studied. The average grain size and the crystallinity results were estimated using X-ray diffraction (XRD) and Raman spectroscopy, respectively. It was found that RTP at 800 °C for 60 s resulted in slightly larger average grain size and higher crystallinity than those without the RTP pretreatment after SPC at 800 °C for 5, 10 and 22 h. The results suggest that the low-temperature short-time RTP pretreatment can promote the crystallization process of the as-deposited a-Si thin films during the following SPC and then improve their crystallinity. Finally, the mechanism is also discussed in detail in the paper.
    Vacuum. 01/2006; 80(5):415–420.
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    ABSTRACT: The electrical properties of cast multicrystalline silicon (mc-Si) contaminated by nickel at different temperatures were investigated by means of scanning electron microscopy and electron-beam-induced current (EBIC). Generally, the recombination activity increased with annealing temperature. In comparison with Czochralski silicon contaminated by nickel, some grain boundaries in nickel-contaminated mc-Si annealed at 500°C also displayed a strong EBIC contrast of about 10%, which suggests a low concentration of nickel in mc-Si can also precipitate or segregate in the defects and increase the recombination strength of defects. Furthermore, nickel tended to precipitate in some special grain boundaries, especially for the annealing at low temperature following slow cool.
    Materials Science in Semiconductor Processing - MATER SCI SEMICOND PROCESS. 01/2006; 9(1):304-307.
  • Zhenqiang Xi, Deren Yang, H.J. Moeller
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    ABSTRACT: The behavior of copper precipitation in cast multicrystalline silicon (mc-Si) annealed at different temperatures under air cooling (30 K/s) or slow cooling (0.3 K/s) was investigated by scanning infrared microscopy (SIRM). Comparing to Czochralski-grown silicon (Cz-Si), copper precipitated more easily in mc-Si, and the lowest temperature of copper precipitation in mc-Si was about 700 °C, lower than that in Cz-Si. It was also observed that copper preferably precipitated on grain boundaries so that near the grain boundaries the denuded zone formed. The results indicate that the defects including dislocations, grain boundaries and microdefects, as the heteronucleation sites, enhanced copper precipitation. Moreover, cooling rates had a great influence on the copper precipitation, especially at lower annealing temperatures. Generally air cooling led to the formation of high density of copper-precipitate colonies.
    Infrared Physics & Technology 01/2006; · 1.36 Impact Factor
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    ABSTRACT: The recombination activity of nickel in p- and n-type Czochralski silicon after rapid thermal process (RTP) in N2, O2 or Ar ambient has been investigated by the microwave photoconductivity decay technique. The effective lifetime of silicon decreases monotonically with increasing nickel in-diffusion temperature, and exhibits a step-like behavior at nickel in-diffusion temperature of 900°C, which indicates that most of nickel atoms precipitate in the bulk no matter what kind of conducting type if the annealing temperature is above 900°C under RTP. It is also found that the ambient during RTP almost has no effect on the recombination activity of nickel in silicon, which suggests point defects almost have no influence on the nickel precipitation.
    Materials Science in Semiconductor Processing - MATER SCI SEMICOND PROCESS. 01/2006; 9(1):296-299.
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    ABSTRACT: The behavior of the copper precipitation in the large-diameter Czochralski silicon (Cz–Si) annealed at 1100 °C followed by air cooling or slow cooling was studied by means of scanning infrared microscopy (SIRM), optical microscopy, and surface photovoltage. For the air-cooled specimen, a high density of copper-precipitate colonies with strong contrast could be easily found in the A-defect zone, while in the D-defect zone of the same specimen almost no colonies could be observed through SIRM. However, optical images showed that the higher density of the etching pits induced by the copper-precipitate colonies occurred in the D-defect zone, which indicates that the copper-precipitate colonies in the D-defect zone was below the detection limitation of SIRM. This suggestion was confirmed by minority-carrier diffusion-length mapping, which revealed that the diffusion length of the minority carriers in the D-defect zone was noticeably lower than that in the A-defect zone. As for the slow-cooled specimen, big star-like colonies formed both in the D-defect zone and A-defect zone, but the diffusion length of the minority carriers in the D-defect zone was also lower than that in the A-defect zone. On the basis of experiments, it is suggested that the as-grown vacancies or their related defects in the D-defect zone enhance the nucleation of copper precipitation either under air cooling or under slow cooling, resulting in the lower diffusion length of minority carriers.
    Journal of Applied Physics 04/2005; 97(9):094909-094909-4. · 2.21 Impact Factor
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    ABSTRACT: The impacts of grain boundary (GB) character and impurity contamination level on the hydrogen passivation of GBs in multicrystalline silicon (mc-Si) were studied by means of an electron-beam-induced current (EBIC) technique. In mc-Si with a low contamination of Fe, the 300K EBIC contrast of all kinds of GBs in the H-passivated state was weak and similar to that in the as-grown state. The 100K EBIC contrast of Σ (Σ=3, 9, and 27) GBs decreased about 75–80%, whereas that of random and small-angle GBs decreased about 35–40%. Due to the different impurity gettering ability of different GBs, the variation in 100K EBIC contrast has suggested that the effect of H-passivation depends on both the GB character and impurity contamination level. In the mc-Si with heavy contamination of Fe, at both 300 and 100K, the EBIC contrast of both Σ (Σ=3) and random GBs decreased but the ratio was
    Physica B Condensed Matter 01/2005; 364(1):162-169. · 1.28 Impact Factor
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    ABSTRACT: The impact of the boundary plane and impurity contamination on the recombination activity of Σ3 boundaries in multicrystalline silicon (mc-Si) was studied by means of electron-beam-induced current (EBIC) technique. In the as-grown contamination-free mc-Si, the EBIC contrast of different Σ3 boundaries was in the order of Σ3{111}<Σ3{110}<Σ3{112}. This order may be attributed to the difference in the defect density of the Σ3 boundaries due to the effect of the boundary plane. But the maximum EBIC contrast did not exceed 2% at 300 K, suggesting that the Σ3 boundaries are originally electrically inactive and the boundary plane has no significant effect on their recombination activity. When contaminated with Fe at 900 °C, the EBIC contrasts of the Σ3{110} and Σ3{112} increased at 300 K, whereas that of the Σ3{111} was still weak (<3%). This variation in the EBIC contrast may be related to the effect of boron and it is also indicated that the Σ3{111} has the weakest gettering ability. When contaminated with Fe at 1100 °C, the EBIC contrasts of all the Σ3 boundaries continued to increase and bright-denuded zones developed around the boundaries. The Σ3 boundaries in the 1100 °C air-cooled mc-Si showed stronger EBIC contrasts and broader denuded zones than those in the 1100 °C quenched one. This phenomenon was explained in terms of the precipitation of Fe. The precipitation of Fe at grain boundaries (GBs) was affected by both the GB type and cooling rate, that is, Fe is easier to form precipitates onto the Σ3{110} and Σ3{112} boundaries during slow cooling.
    Journal of Applied Physics 12/2004; 97(3):033701-033701-5. · 2.21 Impact Factor

Publication Stats

85 Citations
44.54 Total Impact Points

Institutions

  • 2007–2012
    • Zhejiang University of Science and Technology
      Hang-hsien, Zhejiang Sheng, China
  • 2003–2009
    • Zhejiang University
      • • Department of Material Science and Engineering
      • • State Key Lab of Silicon Materials
      Hangzhou, Zhejiang Sheng, China