【作者】 王刚；

【导师】 叶志镇；

【作者基本信息】 浙江大学 ， 材料科学与工程， 2007， 硕士

【摘要】 低维纳米结构是当前纳米科学与技术领域一个重要的研究方向。纳米ZnO材料由于其在电子学、光学和光子学等领域的优异性能而倍受关注，通过Mg掺杂，可以实现对ZnO能带调制作用，从而获得更加广泛的应用。ZnO纳米棒阵列具有负电子亲和力、高机械强度、化学稳定性和相对高效的低电压磷光等特性，在场发射领域有重要的应用价值。本文在综述目前ZnO一维纳米材料的制备方法及掺杂的基础上，选择用热蒸发法，成功制备出两种ZnMgO一维纳米结构，讨论了其形成机理，并研究了其发光性能。通过热蒸发法制备出三种具有尖端形貌的ZnO纳米棒阵列，研究了其场发射性能。其中取得的主要结果如下：1、用热蒸发法制备出ZnMgO纳米棒阵列。ZnMgO纳米棒沿c轴择优生长，直径为100 nm～300 nm，长度约为1μm，为单晶六角纤锌矿结构，Mg的含量为17at％。ZnMgO纳米棒保持ZnO纳米棒常见的六方形貌，但Mg的掺入使六方形貌呈现出一定的不规则性。Mg的掺入产生了210 meV的近带边发射峰的蓝移（室温），实现了对ZnO的禁带宽度的调节。特别地，此方法制备ZnMgO纳米棒阵列具有较好的可重复性。2、用热蒸发法，通过低温—升温—高温三个阶段，首次制备出ZnO／六方ZnMgO／立方ZnMgO异质结构纳米宝塔阵列。纳米宝塔底部直径约600 nm，顶部约70 nm，呈四方形貌。样品中Mg和Zn的平均摩尔比59∶41，且沿着向顶端的方向不断增大，在顶端处达到92∶8。Mg的掺入使近带边发射峰产生了260 meV的蓝移（室温）。纳米宝塔的新颖的结构和生长机理被系统地分析和讨论。3、用热蒸发法制备了三种具有尖端形貌的ZnO纳米棒阵列。三个样品都具有沿c轴择优取向的六方ZnO结构。三个样品的开启场强都在0.5 V／μm以下，性能较好的样品的阈值场强分别约为4.5 V／μm和7 V／μm。F-N拟和良好，确定其为场发射。具有较细尖端的样品表现出较好的场发射性能。用PLD方法预生长的ZnO层减少了衬底上的SiO₂绝缘层，提高了场发射性能。更多还原

【Abstract】 Low-dimensional nanostructures are an important research field in current nano science & technology. Nanostructural ZnO materials have received broad attention due to their distinguished performance in electronics, optics and photonics, and the band-gap can be modulated by doping with Mg for further applications. Aligned ZnO nanorods have important value in filed-emission field due to the properties of negative electron affinity, high mechanical strength, chemical stability and relatively efficient low voltage phosphorescence etc.In this paper, various methods synthesizing one-dimensional pure and doped ZnO nanostructures were summarized. Based upon that, we successfully fabricated two types of ZnMgO one-dimensional nanostructures using thermal evaporation method. The growth mechanisms of the ZnMgO nanostructures were proposed, and their optical properties were investigated. We also synthesized three kinds of aligned ZnO nanorods with abrupt tips using thermal evaporation. And their field-emission properties were investigated. The main results achieved in this dissertation are given as bellow:1. Aligned ZnMgO nanorods were synthesized by thermal evaporation. The ZnMgO nanorods grew along c axis direction of wurtzite ZnO, with diameters ranging from 100 to 300 nm and 1μm lengths. The ZnMgO nanorods have single hexagonal wurtzite structure and the Mg content is 17 at%. As most ZnO nanorods, the ZnMgO nanorods have hexagonal morphology, which isn’t centrosymmetric due to the doping of Mg. A 210 meV blue-shift of near-band-edge emission has been achieved at room temperature, which means the band-gap modulation effect. In particular, this preparation of ZnMgO nanorods array has good repeatability.2. Novel Aligned ZnO/hexagonal ZnMgO/cubic ZnMgO nanopagodas heterostructures were fabricated first, using a simple thermal evaporation method, through processes of low-rising-high temperature. The nanopagodas are about 600 nm at the bottom and 70 nm at the top in diameter. The molar ratio of Mg-to-Znincreases in the nanopagodas along the direction to the tip where it is 92:8, while the average is 59:41. Obvious 260 meV blueshift of the ultraviolet near-band-edge emission has been observed at room temperature. The novel heterostructures and growth mechanism have been analyzed and discussed systematically.3. Three kinds of aligned ZnO nanorods with abrupt tips were synthesized by thermal evaporation. The ZnO nanorods have single hexagonal wurtzite structure and good orientation along c axis direction. The turn-on fields of them are all bellow 0.5 V/μm, while the threshold fields are 4.5 V/um and 7 V/um respectively for the two samples with better performances. The E-J curves are well consistent with the F-N mechanism, which means that the electron emissions are field-emission. The samples with sharper tips have better field-emission property. The ZnO layer, pre-grown by PLD method, decreased the SiO₂ insulating barrier on the substrate, resulting in the improvement of the field-emission property.更多还原