摘要
纳米材料形貌和性能的可控成为新阶段研究的主旋律。本文以ZnO和ZnS纳米材料为研究对象,发展了简便、节能、快速、易于大规模化生产的燃烧法来制备镁或镉掺杂的氧化锌纳米材料,并通过掺杂离子的引入来控制ZnO材料的生长和调节其光学性能。主要成果如下:
1、通过低温燃烧的方法来制备(ZnCd)O,发现Cd在原材料中的加入能够影响产物的形貌,主要生成半卷曲的带状产物。Cd的溶入能够使晶格发生一定程度的畸变而使得E_2~(high)非极性拉曼模式蓝移。5%的Cd掺杂样品600℃退火后由于固溶Cd浓度较高,从而形成一个更深的能级而发出大约600nm的橙红色发射。1000℃退火后,由于Cd的脱溶析出而生成立方CdO相,而使得得带边发射变成双峰发射,可见光区变成与CdO有关的525nm发射占统治地位。无论Cd的含量及退火温度的变化,其带边发光峰没有出现特别明显的红移,这为其以后进一步在紫外发光二极管,紫外激光器方面的应用研究打下基础。
2、通过低温燃烧的方法来制备(ZnMg)O,发现随着Mg在原材料中的加入能够形成卷曲的片状产物。Mg含量较高时会生成宽带隙的Zn掺杂的MgO包裹在Mg掺杂的ZnO外面,而使得发射大大增强。由于带隙紫外发射与绿色发射比例随激发强度的增加而增加,意味着与缺陷有关的绿色发射可能来自近带边的浅施主能级到带双电荷的氧空位跃迁。另外Mg掺杂能够使ZnO带隙发射峰明显的蓝移,特别是高Mg含量时,不仅能调节带隙,而且更能形成量子限域效应而使得带边发射增强。
3、采用简单的无催化剂热蒸发的方法,在水平管式炉中成功地合成二氧化硅均匀包裹硫化锌纳米球结构。通过TEM发现其芯部主要为空心结构,且芯部还存在没被完全还原分解掉的ZnS纳米颗粒或纳米棒,从而导致样品存在460nm的ZnS缺陷光发射。而且这种非晶结构里含有大量的单质微晶硅,从而导致很强的橙红色发射。
For the research on nanomaterials,controlled morphology and modulated performance are attracting extensive interest.The cadmium or magnesium-doped zinc oxide nano--materials prepared by a simple,energy-saving and fast low-temperature combustion method.The introduction of the dopants into ZnO hosts can control the growth and modulate its optical properties.The results will offer a significant help for nanophotonic device applications based on ZnO materials in the future.The main results are as follows:
1.The curled(ZnCd)O ribbons were prepared by a low-temperature combustion approach.The lattice distortion,originating from the introduction of Cd into ZnO, makes the non-polar E_2~(high) Raman scattering mode blueshift.Due to the formation of a deeper level,an orange emission appears at about 600nm in 5%Cd doped-ZnO annealed at 600℃.As the 5%Cd-doped sample annealed at 1000℃,Cd can precipitate from the host and form Zn-doped CdO,resulting into two band edge emission and a predominant green emission of 525nm related to CdO band edge emission Regardless of the Cd content and the annealing temperature,the UV emission does not exhibit obvious redshift.
2.The curled(ZnMg)O sheets were also prepared by a low-temperature combustion approach.As Mg concentration increases,it can precipitate and form Zn-doped MgO with a broader band gap,wrapped Mg-doped ZnO outside.Thus,the near-band-edge emission of Mg-doped ZnO is enhanced greatly due to quantum confinement effect.The emission intensity ratio of the NBE to green increases with increase the excitation power density,indicating that the green emission could originate from the transition from a shallow donor level to Vo~~(++).The high concentration Mg can leads to a significant blueshift of ZnO NBE emission due to alloy effects.
3.Silica coated zinc sulfide nanospheres are successfully synthesized by a simple thermal evaporation method in the tube furnace.The core is mainly a hollow structure by the analysis of TEM.In the nanosphere cores,however,there exsit some ZnS naoparties and nanorods which were not decomposed,resulting into an existence of 460nm light-emitting from ZnS defects.Due to the existence of smaller amorphous Si,a strong orange emission exists in photoluminescence,originating from the band edge emission of Si.
引文
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