上世纪 90 年代初，研究人员在硅片清洗过程中发现了硅的金属催化腐蚀现象。近年 来，凭借工艺简单、操作方便、成本低廉等优点，硅在 HF 溶液中的金属催化腐蚀技术成为 制备硅微纳米结构的常用方法。许多科学家对金属离子及其颗粒在硅表面的沉积和溶解现 象和机制展开了深入研究。通常，硅在 HF 溶液中为各向同性腐蚀，形貌多为多孔结构。但 令人惊喜的是，多个研究表明硅可以在 HF 溶液中可以实现各向异性腐蚀。本论文以硅在 HF 溶液中湿法腐蚀制备微纳米结构为出发点，探究在 HF-氧化剂溶液中制备硅纳米线的形 成机制，通过各种实验手段第一次明确了贵金属在反应过程中的重要作用，推翻了氧化剂 向硅中注入空穴的旧机理。并且受到向硅中注入空穴的启发，发明出一种利用电压调控实 现在 HF 溶液中大规模制备倒金字塔硅纳米结构的新方法。

第一，本论文结合本课题组利用金属催化硅腐蚀现象（MACE）制备硅纳米线技术，通 过一系列的实验手段表征，提出这一技术的新机理模型。不仅银颗粒和硅形成半电池，从 而加快金属颗粒下方硅的溶解；而且银是整个反应的催化剂，整个过程伴随银颗粒的溶解 和银离子的沉积，从而促使腐蚀反应的发生。在反应过程中，是银离子向硅中注入空穴加 快溶解，而不是氧化剂。本文修正了金属和硅界面的电场模型。新理论能更好地解释硅纳 米线的形成机制，为一些新奇的实验现象提供了基础模型。本文还对腐蚀过程中硅银界面 进行了探讨，提出了新的研究方向。

第二，本论文基于硅在 HF 溶液中两步法制备倒金字塔的机理，即在 HF 溶液中，各向 异性腐蚀和空穴注入各向同性腐蚀的协同作用会产生倒金字塔结构，提出利用电压注入空 穴这种调控方式，实现硅在 HF 溶液中制备倒金字塔结构，发现了一种无需借助掩模板，就 能大规模制备倒金字塔的新方法。并且通过改变溶液中离子浓度和电压大小，表征出各向 异性腐蚀和空穴注入各向同性腐蚀对产生倒金字塔形貌的影响，说明两者具有竞争关系。 而向硅中注入空穴有三种方式：氧化剂、在硅片上加正向偏压和光照。本论文研究了在不 同 HF 腐蚀溶液中，根据溶液的不同特点，总结出这三种方式的适用范围条件。

In the early 1990s, the phenomenon of the metal-assisted chemical etching of silicon was discovered during the cleaning process of silicon wafers. In recent years, because of its simplicity, convenience and cost-effectiveness, the metal-assisted chemical etching technology of silicon in aqueous HF solution has become a common technology for making silicon micro/nano-structures. Many scientists have conducted in-depth studies on the phenomenon and mechanism of the deposition and dissolution of metal ions and their particles on the surface of silicon. Generally, the etching of silicon in aqueous HF solution is isotropic, and its morphology is mostly porous after etching. But surprisingly, some studies have shown that the etching of silicon in aqueous HF solution can be anisotropic. Taking the wet etching of silicon in HF solution to making micro-nano structures as the starting point, we explore the formation mechanism of making silicon nanowires in aqueous HF-oxidant solution, and clarify the important role of precious metals in the reaction process through various experimental methods for the first time, while overturning the old mechanism that oxidant injecting holes into silicon. And inspired by the injection of holes into silicon, we invent a new method of using voltage on the silicon wafer to creating inverted pyramid silicon nanostructures in HF solution.

Firstly, based on the metal-assisted chemical etching (MACE), silicon nanowires have been made. We propose a new mechanism model of this technology through a series of experimental means. Not only the silver particles and silicon form a half-cell, which accelerates the dissolution of silicon under the metal particles, but also the silver is the catalyst for the entire reaction. The entire process is accompanied by the dissolution of silver particles and the deposition of silver ions, which promotes the occurrence of etching reactions. During this process, silver ions inject holes into silicon to accelerate dissolution, not oxidizing agents. We modified the electric field model of  the metal and silicon interface. The new theory can better explain the formation mechanism of silicon nanowires and provide a basic model for some new experimental phenomena. We also discuss the silicon-silver interface during the etching process, and submit new research directions.

Secondly, the two-step method of silicon in the HF solution to prepare the inverted pyramid is that the synergistic effect of anisotropic corrosion and hole injection isotropic corrosion will produce an inverted pyramid structure in the HF solution. We use voltage which can inject holes to realize the preparation of inverted pyramid structure from silicon in HF solution. We discover a new method for large-scale preparation of inverted pyramids without the use of masks. And by changing voltage and the ions’ concentration in the solution, the influence of anisotropic corrosion and hole injection isotropic corrosion on the appearance of the inverted pyramid is characterized, indicating that the two are in a competitive relationship. There are three ways to inject holes into silicon: oxidizer, bias on the silicon wafer, and light. According to the different characteristics of various HF solutions, we summarize the applicable scope conditions of these three methods.