【作者】 孙陆威；

【导师】 叶志镇； 何海平；

【作者基本信息】 浙江大学 ， 材料物理与化学， 2011， 博士

【摘要】 低维半导体纳米材料由于其具有独特的理化特性近来得到了人们的广泛关注。半导体纳米线已经成为纳米科学领域内的研究热点问题。基于半导体纳米线的纳米器件已经应用到光电子器件、能量转换、生物医药、光学器件等各个领域。其中,ZnO作为近些年来新兴的一种半导体材料,具有在光电子领域良好的应用前景。我们以ZnO纳米结构为基础,研究了基于ZnO纳米线的Ⅱ型复合纳米结构。Ⅱ型复合结构由于其特有的能带结构,近年来得到了长足的发展。我们在本文中研究一些ZnO基Ⅱ型复合结构的合成、形成机制以及光学性质的例子。本文的主要工作就围绕着以ZnO纳米结构为基础的Ⅱ型复合纳米结构展开。(1)利用化学气相沉积法和溶液法分别合成了ZnO纳米结构,并研究了其光学性质。通过使用MOCVD法生长ZnO仔晶层和溅射的方法生长Au薄膜引导ZnO纳米阵列的生长。通过化学气相沉积法合成了ZnO纳米阵列。在水相和有机相中也分别合成了ZnO纳米结构。在水相中,通过调节还原剂的浓度可以改变纳米线的形貌。在有机相中,通过改变表面活性剂的电性可以调节ZnO纳米结构的形貌。(2)通过荧光发射光谱、激发光谱、瞬态光谱以及变温荧光光谱的手段研究了ZnO:Se纳米棒中的橙光发射。从而说明Se杂质在ZnO橙光发射中的作用,通过一个模型描述了橙光发射的过程。(3)气相法制备了ZnO:Se纳米棒。通过气相沉积的方法合成了ZnO-ZnSe纳米环。通过微观结构分析说明了这个纳米环的形成机制。同时测试了其光学性能,同样发现了很强的橙光发射。我们通过对ZnO-ZnSe之间的能带结构的分析,说明了橙光发射的过程。(4)利用金属辅助刻蚀法合成了硅纳米线阵列。我们研究了硅纳米线的形成过程,金属纳米粒子在刻蚀中的作用以及金属纳米颗粒在刻蚀过程中运动过程。通过对比将硅片浸没在不同浓度的金属离子中和不同的浸泡时间,探讨了由于Ag纳米颗粒的形貌不同导致的最后得到的硅纳米阵列的形貌差异。(5)通过调节刻蚀液中氧化剂的浓度使得硅纳米线表面出线了多孔结构。我们在这种多孔硅纳米线中发现了硅在可见光范围内的荧光发射。我们对比了不同的氧化剂浓度和不同电阻率的硅片中的荧光发射,尝试对这些硅纳米线中的荧光发射现象给予总结。(6)使用金属有机化学气相沉积的方法将ZnO纳米结构包覆到硅纳米线阵列中,研究了不同生长条件得到的两种ZnO纳米结构。对这两种ZnO-Si复合结构进行了结构表征和光学性质的表征。将ZnO包覆到多孔硅纳米线上,使多孔硅和ZnO在可见光区的荧光发射同时出现,得到一个几乎能够覆盖全部可见光区的一条荧光发射谱线。通过对Si-ZnO这种Ⅱ型异质结构能带的分析,说明了ZnO和Si在可见光区内由于能带结构导致的同时发光的原因。更多还原

【Abstract】 Low-dimensional nanomaterials have been attracted due to their unique physical and chemical properties and applications in optoelectronics, energy transfer, biology and medicine and optics. ZnO is an emerging semiconductor with a promising perspective in optoelectronic devices. On the basis of ZnO nanostructures, we studied the type-II heterogeneous nanostructures of ZnO-ZnSe and ZnO-Si, particularly suitable for light emitters due to the type-Ⅱbandgap alignment. In this work, we studied the synthesis, growth mechanism and optical properties of some type-Ⅱheterogeneous nanostructures.(1) ZnO nanowires and nanowire arrays have been synthsized via chemical vapor deposition with the help of ZnO seed layers fabricated by metal organic chemical vapor deposition and Au films deposited by sputtering. ZnO nanostructures are also synthesized by solution methods. In aqueous solution, the size of ZnO nanorods is dependent on the Sodium Citrate concentration. In organic solvent, the morphology of ZnO nanostructures is changed with different surfactants.(2) The high efficient orange emission in ZnO:Se nanorods is discussed with steady emission photoluminescence, excitation photoluminescence, time-resolved photo luminescence and temperature-dependent photoluminescence. Se impurities in ZnO play a critical role in the orange emission. A model is provided to explain the recombination process in ZnO:Se nanorods.(3) The microstructures of ZnO-ZnSe nanorings are studied to explain the growth mechanism. The highly bright orange emission is also observed in the ZnO-ZnSe nanorings.(4) Silicon nanowire arrays are fabricated via metal nanoparticles assisted electroless etching method. The shape of silver nanostructures determines the morphology of as-fabricated silicon nanowire arrays. The evolution of silver nanoparticles depends on the silver ion concentration and immersion periods in silver nitrate aqueous solution.(5) Porous silicon nanowire arrays are fabricated in higher hydrogen peroxide concentration and exhibit an emission band in the range of visible light. Hydrogen peroxide concentration is a key to the orange emission from silicon nanowires. The different resistance of silicon nanowires is responsible for deviation of photon energy in emission bands.(6) ZnO-Si core-shell nanowire arrays and ZnO nanodots decorated on silicon nanowire arrays are prepared by metal organic chemical vapor deposition. The pressure in reaction chamber and reaction periods are responsible for the different morphology of ZnO nanostructures. Furthermore, ZnO layers are coated onto the surface of porous silicon nanowire arrays. A emission band covering entire visible light range is observed in porous silicon-ZnO core-shell nanowire arrays. The type-II bandgap alignment is responsible for the simultaneous emission in silicon and ZnO.更多还原