【作者】 陈江涛；

【导师】 闫鹏勋；

【作者基本信息】 兰州大学 ， 凝聚态物理， 2009， 博士

【摘要】 宽带隙半导体（室温下带隙大于2.0 eV）在蓝紫光和紫外光电子器件，高频、高温、高功率电子器件及场发射器件方面应用广泛。随着科技的发展，对材料的性能要求越来越高如迫切需要能够在高频、高温、大功率以及强辐射下稳定及长期工作的电子器件。氧化锌（ZnO）是一种宽带隙半导体（约3.2 eV），激子束缚能为60meV，室温下非常稳定，具有很高的化学稳定性及很强的抗辐射损伤能力。ZnO在平板显示器、紫外发光二极管、气敏元件、太阳能电池、场发射器件、红外反射器及透明导电薄膜中都有很大的应用前景，因此得到了广泛研究。ZnO是一种无毒，原材料丰富，价格低廉且易于合成的半导体材料，并且容易进行掺杂改性。二氧化锡（SnO₂）也是一种宽带隙半导体，其带隙约3.6 eV且具有更高的激子束缚能130meV，室温稳定并且化学稳定性高。SnO₂广泛应用在气敏元件、太阳能电池及电极材料中。本论文以ZnO及SnO₂纳米材料的制备和应用为背景，以ZnO及SnO₂纳米薄膜、粉体制备及表征为重点，报道了纳米材料领域的研究进展和我们的研究工作，主要研究内容有：1、利用射频磁控溅射法制备Zr掺杂ZnO薄膜。研究发现，掺杂前后的ZnO薄膜在可见光区的透过率均在85％以上。掺杂后，ZnO薄膜带隙变宽，由未掺杂的3.24 eV增大到3.53 eV（9.66 at.％Zr）；相比之下，掺杂样品的形貌有很大变化，由带有“褶皱”的不光滑颗粒转变成光滑且较规则的颗粒。热处理研究发现：未掺杂及掺杂量为1.04 at．％的样品透过率明显下降，低于80％，而掺杂量高于1.04 at．％的样品透过率仍在85％以上，且少量Zr掺杂的样品导电性较好，光学带隙在热处理前后变化不明显。2、利用溶胶-凝胶法制备了稀土元素La掺杂的ZnO纳米薄膜。研究了掺杂量对ZnO结构、形貌及光学性质的影响。掺杂前后ZnO薄膜均为纤维锌矿结构，但结晶变差，晶粒由未掺杂的45 nm减小到10 nm（掺杂量10 at．％）。由于部分La³⁺离子掺入到ZnO晶格当中，光学带隙由未掺杂的3.26 eV增大到3.31 eV，掺杂前后透过率均在85％以上，掺杂样品有所提高。经XPS研究分析，在薄膜表面La元素主要以化合物La（OH）₃的形式存在，表面富含-OH离子。3、结合溶胶-凝胶技术，利用水热法制备了Al掺杂ZnO纳米结构薄膜。研究发现，随着Al掺杂量由0 at．％、1 at．％增大到3 at．％，ZnO的形貌由规则的纳米棒阵列逐渐演变为倾斜的纳米棒、纳米管／棒共存；当含量达到6 at．％时，出现网状结构的ZnO。经XPS分析，ZnO纳米结构中存在少量Al元素，其对ZnO形貌的影响很大。在适量的掺杂浓度下（3 at．％Al），Al（OH）₄^-基团抑制了ZnO沿（002）晶面的生长并对Zn-terminated（002）极性面有腐蚀作用，因此出现ZnO纳米管；而O-terminated（002）极性面为ZnO纳米棒的生长提供形核位置。在紫外Raman光谱中观察到，Al掺杂后，由于Al的存在与材料形貌发生变化，ZnO纳米结构界面处电磁相互作用发生改变，与表面声子有关的模式A₁（LO）振动相应增强。4、利用改进的溶胶-凝胶技术，制备了Eu掺杂SnO₂纳米粉体和多孔膜。系统研究了不同Eu掺杂浓度下，SnO₂粉体的结构及发光特性。用不同的激发光来激发Eu掺杂SnO₂粉体，可发出橙红色和红色可见光。Eu掺杂SnO₂粉体的Eu³⁺离子表现出选择性激发。在间接激发下（紫外光325 nm），光谱以Eu³⁺离子的⁵D₀→⁷F₁跃迁发射为主；而在直接激发下（396 nm和466 nm），以⁵D₀→⁷F₂的跃迁发射为主。经分析⁵D₀→⁷F₁与⁵D₀→⁷F₂的跃迁特点，我们可得到Eu³⁺离子处于不同的位置：取代Sn⁴⁺离子后处于对称性较高的格点处、或处于接近晶粒表面的格点处及晶粒表面。随着格点对称性的不同，Eu³⁺离子表现出选择性激发。此外，在不采用任何模板的情况下，利用sol-gel技术采用旋涂的方法制备了Eu掺杂SnO₂多孔薄膜，对其结构，成分及形貌做了分析。更多还原

【Abstract】 In recent years, significant interest and desire have emerged for the wide-band-gapsemiconductors due to the needs in the optoelectronic devices which can be operate atextreme conditions （e.g. high temperature, high power, high frequence and strongradiation）. In particular, zinc oxide （ZnO） is an oxide semiconductor with awide-band-gap of～3.2 eV, and the binding energy of the exciton is about 60 meV. It isstable at room temperature and has stong anti-radiation ability. ZnO has extensiveapplications and can be used in gas sensors, light emitting diodes, solar cells, fieldemission devices and transparent electrodes. The synthesis process of ZnO is facile andthe precursor materials are rich in the earth and low cost. The doping is an effectivemethod to modify the properties of ZnO. Tin dioxide （SnO₂） is another wide-band-gapsemiconductor （～3.6 eV）, and the binding energy of the exciton is about 130 meV. SnO₂can be also used in many fields as ZnO mentioned above. Recently, SnO₂ attracted manyattentions of the researchers. Against the background of application of functionalmaterials ZnO and SnO₂, this article reports our research on ZnO and SnO₂ nanostructurematerials. The contents are as follows.1. Zr-doped ZnO nano thin films were deposited by radio frequency （RF） magnetronsputtering. The influence of Zr element on the structure, morphology and opticalproperty of ZnO films were investigated. Zr element was doped into ZnO matrix withdifferent contents. The optical band gap has blue shift as increasing Zr content. Andthe morphology of ZnO has much improved. The properties of annealed films werealso studied. The transmittance of the annealed samples （undoped and doped with 1.04at. %） was lower than 70%, but that of samples doped with more Zr element werehigher than 80%.2. Thin films of ZnO with different La doping concentration （0, 1, 3, 5, 10 at. %） arefabricated by sol-gel method using spin-coating technique. The effect of La dopingconcentration on the properties of ZnO films is investigated. The films are hexagonal wurtzite structure and have highly preferred growth along c-axis direction. However, itshows poor crystallization with increasing La concentration and the grain sizes of thefilms decrease remarkably. The optical transmittance of all films is higher than 85% inthe visible region, and doped films become more transparent. The optical energy gapincreases from 3.26 eV to 3.31 eV because some La ions have been incorporated intothe ZnO lattice. The surface chemical state of the films is examined by X-rayphotoelectron spectroscopy （XPS）, and it is indicated that the La element exists mainlyas La（OH）₃ on the film surface.3. Hydrothermal method was used to fabricate undoped and Al-doped ZnO nanostructureson the ITO substrates which pre-coated with ZnO seed layers. The undopedwell-aligned ZnO nanorods were synthesized. When introducing the Al dopant, ZnOshows various morphologies. The morphology of ZnO changes from aligned nanorods,tilted nanorods, nanotubes/nanorods to the nanosheets when the Al dopingconcentrations increases. The Al doping concentrations play an important role on themorphology and optical properties of ZnO nanostructures. The possible growthmechanism of the ZnO nanostructures was discussed.4. The Eu-doped SnO₂ nanocrystalline powders were fabricated by sol-gel calcinationprocess. The effect of the Eu doping concentrations on the structure andphotoluminescence （PL） properties of Eu-doped SnO₂ nanocrystalline powders wasinvestigated. The samples display the reddish-orange light and the red light whenexcited at indirect and direct excitation, respectively. Meanwhile, PL spectra indicatethat the quenching concentrations are different when the excitation wavelength alters.Based on the analysis of the PL spectra, it is believed that Eu³⁺ ions located at differentsites in SnO₂ host are selectively excited. Further, the porous Eu-doped SnO₂ filmswere prepared by spin-coating method. The morphology of the film was dependent onthe calcination temperatures. The structure, morphology and PL property wereinvestigated. The formation mechanism of the porous morphology was also proposed.更多还原