金属-氧化物界面由于在许多先进材料应用中起着重要的作用，如化学催化、光子与微电子器件、纳米结构生长等领域，因而引起了研究者广泛的兴趣。由于金属和氧化物的晶格错配，常在界面处形成台阶、失配位错和周期性结构单元，以释放由错配导致的弹性应变。此外，课题组前期在晶格匹配体系—Au-MgAl₂O₄界面(错配度仅为～0.9%)，观察到界面重构，包含两个原子层厚度的界面超结构(两倍于金晶格基矢)。同时，界面重构可诱导氧化物衬底外延生长成纳米柱，是一种新型的纳米结构生长方式。但是，这种重构界面的超微结构及结构转变过程，尚存在诸多疑点。本文以Au-MgAl₂O₄界面为研究对象，通过改变体系热力学参数控制界面的超微结构；结合消球差扫描透射电子显微术和第一性原理计算获得Au-MgA了₂O₄界面的原子/电子结构；分析氧化物纳米柱的生长机制；以及通过掺杂初步实现对纳米柱的生长控制。本文的研究成果为理解金-氧化物体系的界面重构和相关特性提供新见解，也为调控金-氧化物界面超微结构与合成氧化物纳米结构提供新思路。主要结果如下: 1.对经过不同热处理的Au-MgAl₂O₄界面进行结构表征，根据观察取向相互垂直(即沿＜〓10＞〓与＜11〓＞〓方向)的高角环形暗场扫描透射显微图，在从室温到1100℃的热处理温度范围内，发现界面呈现三种不同的原子组态:共格界面、一层重构界面以及两层重构界面。{111}〓原子面与{111}〓—Al₃终止面毗邻形成共格界面。在{111}〓原子面和{111}〓—Mg-Al-Mg终止面处，存在一个原子层厚度的超结构(两倍于金晶格基矢)。高角环形暗场显微图(原子序数衬度)显示，相对于金晶格，该结构存在周期性的金原子缺失。经过1100℃热处理，在{111}〓原子面和{111}〓—Mg-Al-Mg终止面结合的界面处观察到两层重构原子层，其超结构基矢是金晶格基矢的两倍。随着重构界面的形成，实验观察到界面能的降低。 2.针对第一性原理计算金属-多组元氧化物界面结构过程中存在元素化学势变化难以评估的问题，提出在{111}〓表面附着金原子单层的构想，计算了所有可能的界面模型(共计24种)。结果表明，共格界面和一层重构界面模型能量择优。这两个模型分别与实验观测到的共格界面和一层重构界面一致。在一层重构界面模型基础上，我们提出并优化所有可能的两层重构原子模型(＞10个)，得到最优的两层重构模型，该模型的模拟显微图与实验观察相符。 3.重构界面处的金原子排列方式与尖晶石晶格金属阳离子排列具有强相似性。一层重构界面，金原子按照Al₃层进行排列，相较于{111}〓存在着周期性的缺失；两层重构界面，一层金原子(B层)的排列方式与Al₃层的相似，另一层金原子(A层)和Al、Mg离子呈现类似于Mg-Al-Mg层的排布方式。 4.经热处理后的Au-MgAl₂O₄体系中，金颗粒存在择优取向，即: ORa:{111}〓‖{111}〓&＜〓10＞〓‖＜〓10＞〓 ORb:{115}〓‖{111)〓&＜〓10＞〓‖＜〓10＞〓 ORc:{5 7 13}〓‖{111}〓&＜〓11＞〓‖＜〓10＞〓 ORd:{11 11 1}〓‖{111}〓&＜〓10＞〓‖＜〓10＞〓 其中，ORa为主要取向，两相晶格在界面处完全共格。这些择优取向互为一次孪晶或二次孪晶关系。同时，在金颗粒中观察到大量孪晶。在孪晶面与界面的交点处，常常观察到重构界面的起始或终止以及界面的台阶缺陷。并且，在同样热处理条件下，包含ORb-d择优取向的金颗粒，其诱导产生氧化物纳米柱的高度更高。据此，提出孪晶辅助界面迁移机制。 5.引入Mn元素后可得到更长的纳米柱，甚至是长达十微米的纳米线。纳米柱，具有立方尖晶石结构，高度可达100nm，直径约为60-90nm，呈现两段式生长方式；纳米线，其晶体结构与前者不同，高度可达8μm以上，直径约为100-200nm，并沿生长方向形成贯穿至整个纳米线的层错缺陷。 关键词:Au-MgAl₂O₄界面，金纳米颗粒，界面重构层，孪晶，扫描透射电子显微技术，第一性原理计算

 Metal-oxide interfaces are of great interests to researchers due to that they play key roles in many applications such as chemical catalysis, photonics, microelectronics, and nanostructures growth. The lattice mismatches between metals and oxides often result in the formation of steps, misfit dislocations, and periodic structural units in order to release elastic strains caused by the lattice mismatches. In addition to that, an interface, including two reconstructed atomic layers, was observed in a latticed-matched system of Au-MgAl₂O₄ (only ～0.9% lattice mismatch). Such interface appears with the formation of spinel nanorods, epitaxial to the substrate. However, the detailed structures of this reconstructed interface and related structural transition still largely in the dark. In this thesis, we studied Au-MgAl₂O₄ reconstructed interfaces and tailored the detailed structure by regulating different thermodynamic parameters. Combining with Cs-corrected scanning transmission electron microscopy and first-principle calculations, we obtained atomic/electronic structures of reconstructed interfaces and analyzed related matter transport mechanism for the regrowth of spinel substrate. We also modified the nanostructures through doping method. Our study findings can provide new insights into the chemistry and structure of gold-oxide interfaces and can supply new pathways to tune gold-oxide interfaces and to synthesize oxide nanostructures. The main results are summarized as follows: 1.With different heat treatments, three different reconstructions form over a temperature range from room temperature to 1100℃, namely: a clean interface, a one-layer interface and a two-layer interface, according to the high-angle annular dark field scanning transmission electron microscopy (HAAF-STEM) images from orthogonal view directions (i.e. along <〓10>〓 and <11〓>〓 directions). A clean interface includes {111}〓 atom plane is adjacent to Al₃-termination of {111}〓 surface. One-layer interface exhibits one-monolayer, with significant atomic reconfiguration, between {111}〓 atom plane and {111}〓—Mg-Al-Mg terminated plane. The two-layer interface was observed at the interface between {111}〓 atom plane and {111}〓—Mg-Al-Mg terminated atom plane when temperature is up to 1100℃. With the formation of reconstructed interfaces, it is experimentally observed a decrease of interfacial energy. 2.Whiling carried out first-principles theory simulation, we established the monolayer model, which includes gold atoms of monolayer attached on different terminating planes of {111}〓 surfaces, to avoid the complex issues of evaluating the change in chemical potentials of the involved elements. All possible interfacial models (24 models in total) were calculated and we obtained the preferred interface models—a clean interface model and a monolayer reconstructed interface model, consistent with experimental observations. Based on building monolayer interface model, we proposed and optimized all possible two-layer models (>10) and got a two-layer model with the lowest energy reduction. The simulated images of the model agree with experimental observations. 3.It shows a strong similarity between gold occupancy at interface and metal cations in bulk spinel lattice. The monolayer reconstructed interface includes a gold overlayer with Al₃ atomic layer arrangement and forms periodic vacancies of gold atoms compared with {111}〓 arrangement. The configuration of one gold layer in two-layer interface is similar to that of Al₃ layer. The other gold layer and Al, Mg cations are arranged similarly to that of Mg-Al-Mg layer. 4.There are preferential orientations after heat treatments: ORa:{111}〓‖{111}〓 & <〓10>〓‖<〓10>〓 ORb:{115}〓‖{111}〓 & <〓10>〓‖<〓10>〓 ORc:{5 7 13}〓‖{111}〓 & <〓11>〓‖<〓10>〓 ORd:{11 11 1}〓‖{111}〓 & <〓10>〓‖<〓10>〓 All orientations are first-order or second-order twinned orientations with each other. Meanwhile, a large number of twins were detected in gold nanoparticles. It is always viewed the reconstructed interface starts or ends and has step defects at the intersecting point of twin planes and interface. The oxide bases, underneath the gold particles including ORb-d, are taller compared the case with only ORa. Hence, we proposed the twin-assisted growth mechanism. 5.By adding Mn, longer nanorods, even nanowires with a height up to 10μm, were observed. The growth height of nanorods with cubic spinel lattice structure can reach to 100nm and their diameters are in a range of 60-90nm. The morphology of nanorods suggests a two-stage growth mode. The structure of nanowires is different with nanorods and it is ～8μm in height and ～100-200nm in diameter. Along the growth direction, there are stacking faults throughout the entire length of the nanowire. KEY WORDS:Au-MgAl₂O₄ interface, gold nanoparticles, interfacial reconstructed layers, twins, STEM, first-principle calculations