【作者】 潘楠；

【导师】 侯建国； 王晓平；

【作者基本信息】 中国科学技术大学 ， 凝聚态物理， 2008， 博士

【摘要】 近几年来,ZnO一维纳米结构的制备和物性研究正掀起一股极大的热潮。一维纳米ZnO不仅具有通常一维纳米材料共有的优点,还拥有许多独特、迷人的性质,因而被认为是最重要的无机功能纳米材料之一。实现ZnO一维纳米结构的可控制备和物性调控,不仅可以为我们深入研究介观、量子受限、极化体系中的物理问题提供理想的对象,而且是ZnO基纳米器件走向实用化的基础和必备条件。尽管ZnO一维纳米材料的制备已取得长足的进步,但在制备调控方面依然存在许多令人无法满意之处,对物性调控的研究和理解也十分欠缺。本论文基于ZnO一维纳米材料的气相法制备,以局部调控←→全局调控、生长调控→物性调控、简单体系调控→复杂体系调控这一主线为顺序开展了一系列研究工作,具体包括以下几方面:1.ZnO纳米阵列的可控制备及表征实现对纳米阵列中单个纳米基元尖端形貌和性质有效的局域调控:可控制备出具有不同尖端形貌的ZnO单晶纳米探针阵列,其尖端曲率半径可优于2 nm,具有优异的光学特性和良好的电学特性,而且其光、电性能可通过简单退火处理实现有效调节。实现对纳米阵列有序度的全局调控:可控制备出一种具有十分优异的c轴取向一致性和面内取向一致性的ZnO纳米棒阵列,品质不亚于其单晶外延膜衬底,并优于所有已经报道的（有关ZnO纳米阵列的）结果。2.尺寸效应对ZnO纳米棒发光特性的影响以直径从几百纳米平滑地逐渐收缩到～20 nm、均匀生长的锥形ZnO纳米棒为对象,利用空间分辨阴极荧光谱系统地研究了非量子限域范围1)尺寸调制的表面效应对纳米棒发光特性的调制,以及2)尺寸对纳米棒光学带隙的调制:发现纳米棒的深能级发射主要是来源于表面复合而非体内缺陷,随着纳米棒直径不断收缩,深能级发射越来越占主导地位,而近带边发射被显著抑制,两者积分强度比超线性增加;利用改进的表面复合层近似可以很好地描述该实验结果。发现电子注入对纳米棒的光学带隙有明显的调制作用,随着纳米棒直径不断收缩,近带边发射的峰位反常地移动而且越来越显著;这一现象可以用重掺杂半导体中的Burstein-Moss效应和Band Gap Narrowing效应来解释。3.ZnO纳米阵列的场发射研究以渐变探针、突变探针和平顶纳米棒这三种具有截然不同尖端形貌的ZnO纳米阵列为对象,系统研究了一维纳米结构的尺寸、形貌（特别是尖端形貌）、组装对纳米阵列场发射性能的调制:发现突变探针具有最佳的场发射性能;进一步比较研究了不同的探针形貌对场增强作用和屏蔽效应的调制;提出多级发射探针的设计思路并阐明其优越性。4.高有序度Zn-In-O三维分层纳米结构阵列的可控制备及表征在对本征ZnO一维纳米结构生长调控与物性调控的理解和经验积累基础上,以Zn-In-O为实例研究了ZnO基多元、掺杂纳米体系的生长调控,实现了一种ZnO:In纳米带-（ZnO）_m-In₂O₃超结构纳米柱（m=2,3,4,5）三维分层纳米结构的高有序度阵列的空间自组装,并对该体系做了详细的表征,对其物性和生长机制也做了相应探讨。更多还原

【Abstract】 A tremendous upsurge has seen the studies on the preparation and properties of ZnO 1-dimensional（1-D）nanostructures in recent years.Besides the common virtues addressed on 1-D nanomaterials,ZnO 1-D nanostructures possess many extraordinary, fascinating properties thus have been regarded as one of the most promising inorganic functional nanomaterials.If ZnO 1-D nanostructures are prepared in a controllable way during which the morphology,size,microstructure,composition,orientation（as well as spatial alignment）,and properties can be well controlled,it will be ideal for people to investigate the physics in mesoscopic,quantum-confined,low dimensional, polarized systems,and this is also the prerequisite of putting ZnO-based nanodevices in practice.However,despite the remarkable progresses that have been made in the fabrication of ZnO 1-D nanostructures,most of the present preparation methods are still lack of control.Besides,the studies as well as the understandings on how to efficiently tailor the properties of ZnO 1-D nanostructures are still quite limited.In this paper,efforts will be focused on the fabrication control and properties tailoring of ZnO 1-D nanostructures during vapor phase synthesis process.The framework will be arranged in the order of "local control←→overall control","fabrication control properties modulation",and "binary system→ternary system".The main contents and conclusions can be summarized as the following:1.Controlled synthesis and properties of well-aligned ZnO 1D nanoarraysWell-aligned,single-crystalline ZnO nanoprobe arrays with different tip-shapes were controllably fabricated and the radius of curvature at these tips can be less than 2 nm.The as-grown nanoprobes possess good optical and electrical properties which can be tuned readily by simple air-annealing.Perfectly-aligned,single-crystalline ZnO nanorod arrays with excellent c-axial and in-plane alignment were synthesized controllably.It is found that the quality of alignment of these nanoarrays is as good as the single-crystalline c-GaN epi-layer on which the nanoarrays have grown epitaxially,and is better than any other result on ZnO nanoarrays so far.These perfectly-aligned nanoarrays are excellent candidates for low-threshold,room temperature lasing.2.Strong size effect on the luminescence of individual ZnO nanorodsSingle-crystalline,tapered ZnO nanorods with diameter shrinking smoothly and gradually from several hundred nanometers to～20 nm have been grown controllably. Spatially-resolved cathodoluminescence spectra were collected at spots with different diameters on a series of individual nanorods to study 1)the size-dependent surface effect,and 2)size-induced optical band-gap shift within a non-quantum-confinement region.It is found that the deep level（DE）emission of the nanorods is mainly originated from surface-related recombination process instead of internal defects.As the nanorod diameter continuously shrinks,DL emission becomes more and more dominant while the near band edge（NBE）emission is severely suppressed,with the integral intensity ratio（the ratio of DL to NBE emission）increases superlinearly.These observations can be well-described by an improved surface-recombination-layer approximation.It is found that the injection by electron-beam significantly modulates the optical band-gap in the nanorods.As the nanorod diameter continuously reduced,the peak position of NBE emission shifts anomalously and remarkably.This can be understood by consideration of both Burstein-Moss and Band Gap Narrowing effects which have been observed earlier in those heavily-doped semiconductor systems.3.Morphology dependent field-emission from vertically well-aligned ZnO nanoprobe arraysVertically-aligned single-crystalline ZnO nanoprobe arrays with three different tip-shapes,tapered,abruptly sharpened and flat one,were controllably prepared with wafer size uniformity.The field-emission properties of these nanoprobe arrays were investigated comparatively with the stress on how the geometrical factors such as the tip-shape,radius of curvature at the tip and the density of the nanoprobes affect their field-emission performance.It is found that abruptly sharpened nanoprobe possesses the best field-emission property.Discussion is given on how the screening effect and field enhancement is modulated by the emitter’s shape,which helps us optimize the performance of the nano-emitter via a novel multi-segment design.4.Controlled fabrication and properties of highly-oriented,hierarchical nanobelt-nanopillar arrays from self-assembled ternary oxide Zn-In-OHighly-oriented,hierarchical 3-D nanoarrays of self-assembled ZnO:In nanobelt -（ZnO）_m-In₂O₃（m=2,3,4,5）superstructured nanopillar were grown successfully and repeatably.The morphology,microstructure,composition and optical property are characterized in details.Efforts are made to trace their formation mechanism on the basis of a series of fabrication control processes.更多还原