Microstructure of Nano-porous Silicon and Characteristics of Silicon Electrode Interfaces

多孔硅的孔径尺寸在微米到纳米范围内连续可调，但微结构复杂且不稳定，极大地限制了其应用领域。本论文选择重掺杂n(111)和中等掺杂p(100)单晶硅片为基体，采用电化学阳极极化技术在氢氟酸介质中制备了一系列纳米多孔硅样品，并利用扫描电镜、高分辨透射电镜、拉曼光谱、红外光谱和电子探针微区分析技术以及电化学直流极化、计时电流、计时电位和交流阻抗技术，系统地研究了不同外加电位与电流密度、刻蚀时间、氢氟酸浓度及光照强度与光照时间等条件下制备的多孔硅微结构及化学组成，详细分析了纳米多孔硅的电化学制备参数、硅氢和硅氧含量与晶态结构之间的相互关系，深入研究了单晶硅电极和多孔硅电极的界面特性。 结果表明：纳米...The pore sizes of porous silicon (PSi) can be continuously changed from micrometer to nanometer, however, the applications of PSi have been greatly limited by its nature of complex microstructure and instability. In this work, a series of nano-PSi samples were prepared by anodic polarization on the selected heavily doped n(111)-Si and moderately doped p(100)-Si electrodes under different applied p...学位：理学博士院系专业：化学化工学院化学系_物理化学(含化学物理)学号：2052006015325

Electrochemical Behavior of Porous and Flat Silicon Electrode Interfaces

研究了重掺杂n-型单晶硅(CSi)在氢氟酸体系中生成多孔硅(PSi)的电化学行为,根据线性极化曲线,选取不同的电流密度,采用恒电流阳极极化法,制备了一系列多孔硅层。利用扫描电子显微镜对其进行了表面和断面形貌的表征,通过线性扫描极化技术和计时电位法,比较了单晶硅电极和多孔硅电极的电化学行为,分析了多孔硅形成前后的塔菲尔曲线和计时电位曲线,给出了多孔硅形成过程中的重要电化学参数,如腐蚀电流、开路电位、塔菲尔斜率等。并对其进行深入分析,根据实验结果,提出了单晶硅电极/电解质界面和多孔硅电极/电解质界面的结构模型,并利用该模型讨论了两种电极界面的电化学特性。The electrochemical responses of heavily doped n- type single- crystal silicon(CSi) during the formation of porous silicon(PSi) layers in hydrofluoric acid-based electrolytes were investigated. A series of PSi layers were fabricated by constantly applying different anodic current densities, which were selected according to the linear polarization curve. The surface and cross-sectional morphologies of the PSi layers were studied by scanning electron microscopy. The electrochemical behavior of CSi and PSi electrodes was compared by linear sweep polarization and chronopotentiometry techniques. The important parameters associated with the electrochemical reactions at the electrodes were evaluated by analyzing the Tafel plots and chronopotentiograms obtained before and after the PSi formation. Structural models of the CSi electrode/electrolyte and PSi electrode/electrolyte interfaces were suggested based on the experimental data. Accordingly, the interfacial characteristics of CSi and PSi electrodes were discussed.supported by the National Natural Science Foundation of China(11372263)~

多孔硅的晶态结构与表征方法

多孔硅的生成过程涉及从完美硅单晶逐渐变为不完整晶体,甚至无定形结构,其结构变化取决于制备条件和硅基底的掺杂类型与浓度。多数研究者利用不同的非原位手段研究多孔硅生成过程中晶态结构的变化,进一步研究其光致发光性能。本文对不同条件下生成的多孔硅的晶态结构进行了归纳总结,比较了透射电子显微镜、X射线衍射技术及拉曼光谱技术3种表征方法的特点及其对晶态结构认识的影响,指出不同微观表征手段的局限性使得众多的报道结果相差较大。最后本文就该领域的发展趋势和急需解决的问题进行了总结

Crystalline Structures and Characterizations of Porous Silicon

The formation of porous silicon (PSi) involves the transition from perfect monocrystalline silicon to non-perfect crystalline such as polycrystalline or even amorphous structures, depending strongly upon the fabrication conditions and the nature of silicon substrates. Significant effort has been made to employ various ex-situ methods to study crystalline transformation in order to understand the photoluminescence (PL) of PSi. This paper summarizes the crystalline structures of PSi fabricated at different conditions, and compares the advantages of various characterization techniques. TEM can directly observe the crystalline structures of PSi, but suffers difficulties in the preparation of TEM samples and the possible introduction of amorphous contents. The information of the inter-planar distance and the crystallite size of PSi can be obtained from XRD, while the pore structures (pore wall and size) based on the proposed structural model can be obtained from small angle X-ray scattering method, with more detailed information about the coordination atoms is available from X-ray absorption fine structure method. Raman spectroscopy is proved to be a non-destructive and quantitative method to characterize the microstructure of PSi when combined with the corresponding models. Finally, the current problems and future researching trends in the crystalline structures and their characterizations of PSi will be briefly mentioned

硅片表面多金属污染的交流阻抗表征

在接近氢氟酸实际应用浓度条件下,利用交流阻抗技术研究了硅片表面金属微观污染行为,在氢氟酸溶液中分别加入0.5和1μg/g的铜、铁、镍、钙四种金属离子,获得了硅片在单金属溶液中的特征交流阻抗谱,并在此基础上研究了三种金属及四种金属共存时的特征交流阻抗谱,通过等效电路的拟合估算了硅/氢氟酸界面电化学反应的动力学参数,并结合扫描电镜形貌图探讨了不同类型的单金属和多金属对硅电化学行为的影响.结果表明,多金属微观污染是各种单金属协同作用的结果,铜在硅片上发生电化学沉积,直接导致硅片表面粗糙化.铁对硅片表面的破坏严重,同时影响铜的沉积.镍的存在使硅片表面更容易氧化.而钙通过在硅片表面形成氟化钙沉淀物可以钝化表面,减缓铜在硅片表面的沉积

Multi-metal Microcontamination of Silicon Wafer Surface Characterized by Electrochemical Impedance Spectroscopy

The multi-metal microcontamination of silicon wafer surface was studied by electrochemical impedance spectroscopy (EIS) under the metallic impurity concentrations close to the practical applications (mu g/g level) based on the one-metal microcontamination effect. The characteristic EIS spectra were measured in the HF solutions containing one and three or four different metals simultaneously at the levels of 0.5 and 1 mu g/g, respectively. The kinetic parameters of electrochemical reactions at the Si/HF interface were evaluated by the equivalent circuit. The effects of single or multi-metal types on the electrochemical behaviors of silicon were also investigated in combination with SEM observations. Silicon surface became rougher by copper deposition, which is directly accelerated in the presence of iron and nickel by corroding the Si surface and by increasing the charge density of Si surface, respectively, while reduced by calcium due to the formation of CaF2, which acts as a passivated Surface to delay copper deposition

Transformation of Crystalline State during Porous Silicon Formation

采用电化学阳极氧化法,对p型单晶硅施加30 mA/cm~2的恒定电流密度,在40%氢氟酸溶液中和氮气保护气氛下分别极化为1,3和5; min,制备不同生长阶段的多孔硅样品,并对新鲜样品进行表面形貌观测及微观结构表征,获得从单晶硅到多孔硅形成过程所涉及的各种晶态组成的相对比例。结; 果表明,不同极化时间制得的单晶硅表面均形成了海绵状均匀分布的纳米孔洞结构。在多孔硅的形成过程中,单晶硅结构发生了显著的晶态转变和晶粒尺寸变化,导; 致大单晶、纳米晶和无定形态并存,晶粒直径从初期的1.41 nm减小到并保持在0.65; nm,而晶态的转变和晶粒尺寸的变化被认为与晶格畸变程度有关。The porous silicon samples were fabricated on the p-type single crystal; silicon wafers in 40% hydrofluoric acid solution under a nitrogen; atmosphere by applying a constant current density of 30 mA/cm~2 for 1, 3; and 5 min, respectively. The surface morphologies and microstructures of; the freshly prepared porous silicon layers were investigated. The; relative amounts of large single crystal, nanocrystalline and amorphous; silicon related to the extent of crystallinity transformation and the; change of crystallite diameter involved during porous silicon formation; were evaluated via multi-peak fitting Raman spectra. The results reveal; that the sponge-like nanoporous structures are formed on the silicon; surfaces at different polarization time. The apparent changes in crystal; structure and crystallite diameter occur during the porous silicon; formation, leading to the coexistence of large single crystal,; nanocrystalline and amorphous silicon. The crystallite diameter reduces; to 0.65 nm from 1.41 nm for the initial regime.The degree of lattice; distortion could be contributed to the crystallinity and crystallite; diameter.国家自然科学基金项目; 福建省特种先进材料重点实验室开放课题资助项

Measurement of integrated luminosity of data collected at 3.773 GeV by BESIII from 2021 to 2024

We present a measurement of the integrated luminosity e+e- of collision data collected by the BESIII detector at the BEPCII collider at a center-of-mass energy of Ecm = 3.773 GeV. The integrated luminosities of the datasets taken from December 2021 to June 2022, from November 2022 to June 2023, and from October 2023 to February 2024 were determined to be 4.995±0.019 fb-1, 8.157±0.031 fb-1, and 4.191±0.016 fb-1, respectively, by analyzing large angle Bhabha scattering events. The uncertainties are dominated by systematic effects, and the statistical uncertainties are negligible. Our results provide essential input for future analyses and precision measurements