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水热合成ZnO稀磁半导体的研究-李慧勤-2008

2013年06月17日 11:52 Diluted magnetic semiconductors (DMS) is a kind of material that it can successfully combine the mag 点击:[]

 

 作者姓名  李慧勤
 中文论文题名  水热合成ZnO稀磁半导体的研究
 外文论文题名  Preparation of ZnO Diluted Magnetic Semiconductors by Hydrothermal Method
 论文提交日期  2008-06-17
 学位年度  2008
 中文论文关键词  稀磁半导体,ZnO,水热合成,磁性能
 外文论文关键词  Diluted Magnetic Semiconductors, ZnO, hydrothmal synthesis, magnetic performance

 

中文论文文摘


    稀磁半导体(Diluted Magnetic Semiconductors-DMSs)材料同时具有电子的电荷属性和自旋属性,是自旋电子学的基础,具有优异的磁、磁光、磁电性能,使其在高密度非易失性存储器、磁感应器、半导体集成电路、半导体激光器和自旋量子计算机等领域有广阔的应用前景。
    实验以ZnO作为基体,采用水热法分别进行了Ni2+、Cr3+、Co2+和Mn2+的掺杂,制备ZnO基稀磁半导体粉体。讨论了前驱物制备方法、搅拌时间、反应温度、反应时间、矿化剂种类和浓度、掺杂含量等工艺因素对粉体制备的影响。通过XRD表征粉体的晶相,对样品进行扫描电子显微镜分析,观察粉体的显微结构;通过紫外吸收测试掺杂离子的吸收峰,并且通过计算出的禁带宽度,可以检测掺杂对ZnO电性能的影响;磁滞回线测试ZnO基稀磁半导体材料的磁滞回线,分析材料的磁性能;通过EDS能谱测试分析掺杂的实际含量。
    对于Ni2+掺杂ZnO,NaOH作为矿化剂比KOH更合适掺杂的进行;高浓度的矿化剂浓度下,有利于形成纯净的晶体,3mol/L为宜;但矿化剂浓度不宜过高,当浓度为5mol/L时,出现了Ni(OH)2杂质相。讨论了不同掺杂含量对制备样品的影响,当x=0.05和0.1时,得到了纯净的晶相;当掺杂含量依次为x=0,0.05,0.1,0.2时,禁带宽度先降低后升高,分别为3.20eV,3.19eV,3.15eV,3.17eV。分别采用沉淀法和Sol-gel法制备前驱物,沉淀法所制备前驱物,经水热合成的粉体较为理想,可以得到纯净的Zn0.95Ni0.05O样品,XRD和UV-Vis证实Ni2+取代了Zn2+,晶体具有铁磁性,实际的掺杂含量为3.20%(Atomic%)。
    对于Cr3+离子掺杂ZnO,NaOH做矿化剂比KOH更有利于离子的掺杂;升高反应温度有利于掺杂的进行,在240℃为宜;反应时间为24h、搅拌时间7~8h有利于合成颗粒小的晶粒;而当掺杂含量增大时,会出现杂质相,说明ZnO对Cr离子的固溶是有限的;矿化剂是3mol/L的NaOH,填充率为75%,Cr的掺杂量不高于0.15mol比时可得到的性能较好的稀磁半导体,XRD测试表明随着Cr离子的掺杂量有限,当x≤0.15时,掺杂进入到ZnO的晶格之内,并且所制备的晶体发育比较完整。从FE-SEM可以观察出,掺杂量x≥0.2时,晶体的形貌从短柱状转变为长柱状。由磁滞回线表明,晶体呈现顺磁性。
对于Co2+掺杂ZnO,在200ºC 和240ºC的条件下,可以合成比较纯净的Zn0.95Co0.05O和Zn0.9Co0.1O晶相;UV-Vis测试发现在570nm, 610nm and 655 nm处分别出现了Co离子的吸收峰,说明Co离子掺杂进入到ZnO的晶格内;在室温下,晶体呈现顺磁性。
    对于Mn2+掺杂ZnO, 矿化剂浓度影响产物的浓度,以3mol/L 的NaOH作为矿化剂,合成出了比较纯净的Zn0.95Mn0.05O和Zn0.9Mn0.1O晶相;以5mol/L的NaOH作为矿化剂,可以合成Zn0.85Mn0.15O晶体。室温下,Zn0.9Mn0.1O和Zn0.85Mn0.15O晶体呈现铁磁性。

 

外文论文文摘


    Diluted magnetic semiconductors (DMS) is a kind of material that it can successfully combine the magnetism and electronics in a single substance. DMS is recognized as the base of spin-electron theory, which has some good magnetic performance, magneto-optic and magneto-electric nature,which made its widespreadly applied in such fields as high density nonvolatile memory, magneto-inducer, semiconductor integrated circuit, semi- conductor laser, spin quantum computer, and so on.
    ZnO matrix diluted magnetic semiconductor crystals were prepared by hydrothermal method doped with Ni2+、Cr3+、Co2+ and Mn2+ doped. Some process factors were studied such as different prescour preparation, mixing time, reaction temprature, reaction time, mineralizer type and its concentration and doping content, etc. XRD and UV-Vis were employed to demonstrate the presence of doped ions in substitution of Zn sites. FE-SEM images show as-prepared samples crystals pattern. UV-Vis measurements demonstrate the presence of doped ions in substitution of Zn2+ and forbidden band width can be calculated. EDS patterns show the actual doping concent of the final product. Room temperature VSM reveals magnetic properties of the samples.
Zn1-xNixO diluted magnetic semiconductor was prepared by hydrothermal method with the Ni2+ of 5%~20%(Atomic%). NaOH of 3mol/L were used as the mineralizer. Ni(OH)2 phase appeared when the concentration of NaOH up to 5 mol/L. The forbidden band width were sequentially 3.20eV,3.19eV,3.15eV and 3.17eV with doping content x=0,0.05,0.1 and 0.2, only when x=0.05 and 0.1, as-prepared samples were good. The pure Zn0.95Ni0.05O was obtained with prescour prepared by method of precipitation. XRD and UV-Vis are employed to demonstrate the presence of Ni2+ in substitution of Zn2+ sites. XRD analysis indicates that the as-prepared Zn0.95Ni0.05O has the pure ZnO wurtzite structure. UV-Vis measurements demonstrate the presence of Ni2+ in substitution of Zn2+. Room temperature VSM reveals a ferromagnetic loop of the Ni-doped ZnO samples and EDS shows actual content of Ni2+ is 3.20%(Atomic%)。
    Zn1-xCrxO diluted magnetic semiconductor was prepared by hydrothermal method at 240 ºC for 24h with NaOH of 3mol/L was used as the mineralizer. The best mixing time is 7h~8h and the compactness is 75%. Impurity phase would increase with Cr3+ concent from 0.05 to 0.20. X-ray diffraction measurements indicates that the as-prepared Cr-doped ZnO (x=0.05,0.1,0.15) has the pure wurtzite structure which demonstrates the presence of Cr3+ in substitution of Zn2+. FE-SEM analyses show that nanocrystalline powders changing from short stylolitic structure to long stylolitic structrue when the Cr3+ concentration of x≥0.2. Room temperature VSM reveals a weakly paramagnetism loop.
    Zn1-xCoxO diluted magnetic semiconductor was prepared by hydrothermal method at 200 ºC and 240 ºC for 24h with the Co2+ doping content of 5%~15%(Atomic%). NaOH was used as the mineralizer. X-Ray Diffraction (XRD) spectras indicate that the as-prepared Co-doped ZnO had the pure ZnO wurtzite structure. UV–Vis spectroscopy shows that the Co2+ are substituted to Zn2+ in ZnO matrix and its peak value appears at 570nm, 610nm and 655 nm. Room temperature VSM reveales a paramagnetic loop of the Co-doped ZnO samples. FE-SEM analyses explay that nanocrystalline powders of pure Zn095Co0.05O and Zn09Co0.1O could be prepared by the hydrothermal method.
    Zn0.95Mn0.05O and Zn0.9Mn0.1O crystals were synthesied by hydrothermal method at 240ºC with NaOH of 3mol/L. Zn0.85Mn0.15O crystals were prepared by hydrothermal method at 240ºC with NaOH of 5mol/L. Zn0.9Mn0.1O and Zn0.85Mn0.15O crystals appeare ferromagnetic property at room temprature.

    

 

 

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