【作者】 武立立；

【导师】 张喜田；

【作者基本信息】 哈尔滨工业大学 ， 光学， 2014， 博士

【摘要】 宽禁带半导体ZnO纳米结构的制备及应用是当今材料领域的研究热点之一。由于III族元素是ZnO最好的n型掺杂剂，探索III族元素相关的ZnO基纳米材料的制备，研究其潜在的物理、化学新属性，发展其相关的器件应用，无论在科学研究还是实际应用中均具有重要意义。III族元素在ZnO结构中的引入，可能与N共掺杂实现p型导电，也可能引起微观结构的变化，形成孪晶或InMO3(ZnO)m (M=In, Ga; m为整数)超晶格结构。因此，本论文采用化学气相沉积方法，合成了N-In共掺杂的ZnO纳米带、In/Ga掺杂的ZnO孪晶纳米结构以及InMO3(ZnO)m超晶格纳米结构，并研究了它们的物理性质。具体包括以下几个方面：研究了N-In共掺杂的ZnO纳米带的制备及光学性质。采用化学气相沉积方法合成了N-In共掺杂的ZnO纳米带。利用扫描电子显微镜、X射线能谱仪和微区拉曼光谱仪分别对合成纳米带的形貌、成分和拉曼光谱进行了分析，确定了纳米带的结构和成分。通过与未掺杂和In掺杂的ZnO低维纳米结构进行比较，拉曼光谱和光致发光谱同时证明了N的存在，确定合成产物为N-In共掺杂ZnO纳米带。纳米带的低温光致发光谱中，中性受主性束缚激子的发光峰占主导地位，受主为N与In元素形成的2NO-InZn受主复合体，复合体的受主束缚能约为112meV。研究了ZnO孪晶纳米结构的制备及光学性质。采用化学气相沉积方法合成了两种形貌新颖的ZnO孪晶纳米结构：一种是由三根简单纳米带同轴共生形成的In掺杂ZnO三刃纳米带；一种是由六角纳米片按一定规律组装在一起形成的In、Ga掺杂的ZnO串状六角片。利用扫描电子显微镜、X射线衍射仪和透射电子显微镜对纳米结构的形貌、晶体结构和微观结构分别进行了表征。两种纳米结构虽然具有不同的形貌，但均具有ZnO六角纤锌矿结构，构成两种纳米结构的基本单元的宽表面均为±(0001)面，且互成64o或116o，通过(0113)和(0111)孪晶界沿[2110]方向被组装在一起。基于两种纳米结构的形成过程，在Quadra孪晶核模型的基础上提出了(0113)和(0111)孪晶结构的形成机制。两种孪晶纳米结构的光致发光谱均由紫外发光峰和可见发光带两部分组成。可见发光明显强于紫外发光是由于结构中大量孪晶的出现所致。本研究内容为将简单纳米结构单元组装成复杂结构提供了一个新的方法，有利于高密度集成纳米功能器件的早日实现。研究了In2O3(ZnO)m材料的晶体结构和电子结构。应用第一性原理密度泛函理论提出了新的原子排布规则，构建了具有W调制结构的基态晶体结构模型。W调制结构的夹角对于不同的m值保持不变，而调制结构的周期性与m值成正比。W调制结构的稳定性明显优于“一”字形结构模型。通过对结构中电子态密度的计算，认为In2O3(ZnO)m的电子传输特性由In-5s和Zn-4s电子态决定。研究了ZnO/In2O3(ZnO)m异质结纳米带的制备及弯曲机制。采用化学气相沉积方法合成了ZnO/In2O3(ZnO)m (m=4,5)异质结纳米带。利用扫描电子显微镜、X射线能谱仪和透射电子显微镜对纳米结构的形貌、成分和微观结构分别进行了表征，纳米带呈弯曲状，由具有In2O3(ZnO)m超晶格结构的外弧部分和具有ZnO六角纤锌矿结构的内弧部分组成，两者通过(0001)面外延生长在一起。ZnO和In2O3(ZnO)m两种材料由于晶格常数的不同，在界面处产生了明显的晶格失配，因而引入弹性应变。这些应变，一部分通过在界面处形成位错进行了释放；其余部分则通过弯曲的形式进行释放，弯曲程度与纳米带的厚度有关。研究了In2-xGaxO3(ZnO)m四元超晶格纳米带的制备及场发射特性。通过优化实验参数，在三元超晶格的基础上，合成了具有不同Ga浓度的In2-xGaxO3(ZnO)m四元超晶格纳米带。应用X射线衍射仪、X射线能谱仪、元素分布图、X射线光电子能谱仪、超薄纳米切片技术和高分辨透射电子显微镜对纳米带的晶体结构、成分和微观结构分别进行了分析，证实了In2-xGaxO3(ZnO)3四元超晶格结构的形成。其X射线衍射的结果补充了粉末衍射标准联合委员会数据库中关于In2-xGaxO3(ZnO)3四元超晶格材料的相关数据。X射线光电子精细谱中，Zn-2p和In-3d的峰位向高能侧移动，而Ga-3d的峰位则向低能侧移动，说明In2-xGaxO3(ZnO)3结构中的电子由Zn和In向Ga原子过渡，引起了各元素有效电荷密度的变化。对In1.63Ga0.37O3(ZnO)3纳米带的场发射特性进行了研究，纳米带的开启电场为4.1V/μm、增强因子为1059，电流密度在应用电场为10V/μm的条件下、在4500秒内没有出现任何的衰减和震荡，表现出良好的稳定性。更多还原

【Abstract】 ZnO is a wide-band-gap semiconductor. The research on the synthesis and application of ZnO nanostructures is one of the hot topics in material science. The exploretion of ZnO based nanostructures related to group III elements on their growth, potential physical and chemical properties and device applications has important significance not only to scientific research but also to practical application, because group III elements are the best n type dopants for ZnO. The introduction of group III elements into the structure of ZnO may provide an effective way to obtain p type ZnO material by codoping with element N, or lead to the changes of microstructure and cause the formation of twinning structure or InMO3(ZnO)m (M=In, Ga; m is integer) superlattice structure. In this thesis, N-In codoped ZnO nanostructures, In/Ga doped ZnO twinning nanostructures and InMO3(ZnO)m superlattice nanostructures are prepared in a controlled chemical vapor deposition process. Systematical studies on their preparation and properties are carried out. Major attention is paid to the following aspects:The synthesis and photoluminescence properties of N-In codoped ZnO nanobelts were investigated. N-In codoped ZnO nanobelts were prepared via chemical vapor deposition method. The morphology of the products was characterized by scanning electron microscopy (SEM), and the chemical composition of the products was analyzed by energy dispersive X-ray (EDX). Compared with undoped and In doped ZnO nanostructures, the appearance of the Raman shift at279cm-1in the Raman spectrum confirms that N is introduced into In-doped ZnO nanobelts and the products are N-In codoped ZnO nanobelts. The temperature dependent PL spectra and excitation power-dependent PL spectra at9K indicate that2No-InZn acceptor complexes are formed in N-In codoped ZnO nanobelts, the energy level of2No-InZn acceptor complex should be about112meV.The synthesis and photoluminescence properties of ZnO twinning nanostructures were investigated. Two kinds of ZnO twinning nanostructures with novel morphology were prepared by chemical vapor deposition method: one is In-doped ZnO three-edged nanobelt, and the other is In/Ga doped hexagonal-disk string. These nanostructures were characterized by SEM, X-ray powder diffraction (XRD), transmission electron microscopy (TEM). Although they have different morphologies, the two kinds of nanostructures have the same microstructures. They are both wurtzite structures of ZnO. The top/bottom surfaces of their building blocks, nanobelt or nanodisk, are the (0001) crystal plane. These building blocks are connected by {0113} and {0111} twin planes along [2110] direction. The intersection angle of different building blocks is64o or116o. According to the analysis of these twinning structures, the growth mechanism of (0113) and (0111) twin structure is proposed based on the Quadra model. The photoluminescence spectra of these two ZnO twinning nanostructures both consist of a UV emission peak and a broad emission band in visible region. The emission in visible region is stronger than that in UV region. This may be related to the formation of abundant twinning structures. The research work in this part may provide an effective path for assembling one-dimensional nanostructures into well-ordered, sophisticated nanostructures, which is helpful to achieve high density integrated optoelectronic circuits.The crystal and electronic structure of In2O3(ZnO)m were investigated by first principles. New atomic arrangement rules and ground state structural model for In2O3(ZnO)m were proposed. Zigzag modulated structure is believed to exist in the structure of In2O3(ZnO)m. The angle of Zigzag modulated structure remains the same, and the periodicity of the zigzag shape is linear to the value of m. The formation energy of In2O3(ZnO)m for the zigzag model is much smaller than that in the flat boundary structure model. The transmission of electron in the structure of In2O3(ZnO)m is related to the In-5s, and Zn-4s states.The synthesis and bending mechanism of ZnO/In2O3(ZnO)m heterostructure nanobelts were investigated. ZnO/In2O3(ZnO)m (m=4,5) heterostructure nanobelts were prepared by chemical vapor deposition method. The morphology, ingredient, and microstructure of the nanobelts were characterized by SEM, EDX, and TEM. The nanobelts are bent in shape, and consist of an In2O3(ZnO)m subnanobelt and an ZnO subnanobelt. The outer subnanobelt is In2O3(ZnO)m, and the inner subnanobelt is ZnO. The two parts share the common (0001) plane. The different lattice constants for In2O3(ZnO)4and ZnO result in a lattice mismatch and introduces strain. In this case, the strain at the (0001) interface is released by the creation of mismatch dislocations and formation of the bent shape. The radius of curvature of ZnO/In2O3(ZnO)m heterostructure nanobelts is a function of their thickness.The synthesis and field emission properties of In2-xGaxO3(ZnO)m nanobelts were investigated. In2-xGaxO3(ZnO)m nanobelts were prepared by introducing element Ga into the structure of In2O3(ZnO)m. Those nanobelts were characterized by XRD, EDX, element mapping, X-ray photoelectron spectra (XPS), and HRTEM, confirming the formation of In2-xGaxO3(ZnO)3superlattice structure. The calculated XRD results enrich the JCPDS database. In XPS survey spectra, the binding energies of the Zn-2p and In-3d peaks both exhibit a positive shift in comparison to the standard values, while the binding energy of Ga-3d peak exhibits a negative shift. This could be attributed to the change of effective charge density of In2-xGaxO3(ZnO)3caused by an electron transfer from Zn and In to Ga. Field-emission measurements of In1.63Ga0.37O3(ZnO)3nanobelts were carried out, showing good field-emission performances. The turn-on electrical field is as low as4.1V/μm; and the field enhancement factor is1059. The emission current density shows a good stability for4500seconds without any current degradation or notable fluctuation.更多还原