【作者】 夏振波；

【导师】 王业伍；

【作者基本信息】 浙江大学 ， 凝聚态物理， 2011， 硕士

【摘要】 氧化锌(ZnO)是一种直接宽带隙半导体,其室温禁带宽度为3.37eV,激子束缚能为60meV。由于ZnO的激子能够在室温下稳定存在,因而被认为是替代GaN的制备光电器件的理想材料。本文主要采用水热法可控生长氧化锌微纳米材料,在此基础上研究其光学、电学及磁学性质。首先,我们通过调控生长条件分别制备了氧化锌微纳米柱、微纳米柱薄膜、多孔球和多孔薄膜,并深入探讨了其生长机理我们发现衬底上的氧化锌籽晶层和反应前驱液中柠檬酸钠在反应过程中起着决定性的作用：衬底控制着成核过程,而柠檬酸钠则决定了产物的晶相。因此,我们通过控制氧化锌籽晶层和反应前驱液成分,就可以非常容易地选择性生长氧化锌微纳米柱、阵列薄膜、多孔球以及多孔薄膜的方法。接着我们研究了微纳米柱薄膜的导电性能,实验结果表明该薄膜具有优良的导电特性,其载流子迁移率达到了54.8 cm2·V-1·s-1,载流子浓度为-2.73×1018cm-3。简单的工艺,低廉的成本以及突出的电学性能将会使这种结构具备极大潜在应用价值。为了深入了解这种材料的导电机制,我们分别利用光致发光谱,电子顺磁共振谱和X射线光电子能谱,对样品进行了详细地分析,结果表明样品中存在大量的间隙氢缺陷,这可能是微纳米柱薄膜n型载流子的来源。另外我们研究了氧化锌多孔球的光学及磁学性能。通过热分解新型的多孔材料(Zn5(OH)8Ac2·2H2O, LBZA)就可获得具有巨大比表面积(42m2/g)的氧化锌多孔球,这种结构的氧化锌还未见报道。更有意思的是我们发现氧化锌多孔微球具有比较弱的室温铁磁性。我们利用XPS, EPR, PL和SQUID等分析测试手段对这种球状氧化锌的微观结构和物理性质进行了系统的测试和分析,试图探究其室温铁磁性的来源。实验结果表明,未掺杂氧化锌多孔球的室温铁磁性能来源于一种浅施主能级缺陷,位于表面处以氢锌键形式存在的氢缺陷可能就是这种浅施主缺陷。更多还原

【Abstract】 Zinc Oxide is a kind of semiconductor with a direct band gap of 3.37 eV at room temperature and exciton binding energy of 60 meV. On behalf of the large exciton binding energy, the exciton can keep stable under room temperature, which makes it potential for blue-ultraviolet and white light-emitting devices, as a substitution of GaN.In this thesis, the growth of micro/nano ZnO material was controlled by hydrothermal method and their optical, electrical and magnetic properties were studied. After the ZnO micro-/nano-rods, rods based thin film, porous spheres and porous film were successfully fabricated by controllable growth process, we figured out the growth mechanism of these structures. Both the substrate coated with ZnO seed layer and sodium citrate in the precursor solution played a key role in leading the products. The citrate anions not only modify the morphology but also decide the phase of the grown zinc compounds. The ZnO thin layer coated on glass substrate is used to control the nucleation event and finally modifies the morphology of the grown ZnO. In conclusion, we can selectively grow the four kinds of structures mentioned above through the control of ZnO seed layer and precursor solution.We continued to study the conduction of nano rods based thin film, and it was found to have predominantly electrical properties. Its carrier mobility is as high as 54.8 cm2·V-1·s-1 and concentration-2.73x1018 cm-3. Simple growth process, low cost and superior conductivity make this film of great potential for practical application. In order to understand the mechanism of conduction, photoluminescence, electron paramagnetic resonance, Fourier transform infrared spectra and X-ray photoelectron spectroscopy were used to analyze its crystal structure and internal properties. A high concentration of interstitial hydrogen existed on the surface of nano rods, which may be the source of most carriers in the film. We also studied the optical and magnetic properties of the ZnO porous spheres. They can be obtained through thermal decomposition of Zn5(OH)8Ac2·2H2O or LBZA, which was reported for the first time. The BET surface area of this kind of ZnO reached 42 m2/g. It’s interesting that porous ZnO shows significant room temperature ferromagnetic even without any transition metal doping. In order to found out the origin of the room temperature ferromagnetic, we systematically analyze its micro structure and related physical properties with the help of X-ray photoelectron spectroscopy, electron paramagnetic resonance, photoluminescence and SQUID. It turned out to be the shallow donors caused by hydrogen perhaps play an important role in triggering magnetic order in ZnO samples. Hydrogen should be located on the surface of the material combined with the atom of zinc.更多还原