Title: Wafer-Scale Fabrication of Hierarchically Porous Silicon and Silica Glass by Active Nanoparticle-Assisted Chemical Etching and Pseudomorphic Thermal Oxidation Show Chinese title

Title: 通过活性纳米粒子辅助化学蚀刻和拟态热氧化实现分层多孔硅和二氧化硅玻璃的晶圆级制造

Abstract: Many biological materials exhibit a multiscale porosity with small, mostly nanoscale pores as well as large, macroscopic capillaries to simultaneously achieve optimized mass transport capabilities and lightweight structures with large inner surfaces. Realizing such a hierarchical porosity in artificial materials necessitates often sophisticated and expensive top-down processing that limits scalability. Here we present an approach that combines self-organized porosity based on metal-assisted chemical etching (MACE) with photolithographically induced macroporosity for the synthesis of single-crystalline silicon with a bimodal pore-size distribution, i.e., hexagonally arranged cylindrical macropores with 1 micrometer diameter separated by walls that are traversed by mesopores 60 nm across. The MACE process is mainly guided by a metal-catalyzed reduction-oxidation reaction, where silver nanoparticles (AgNPs) serve as the catalyst. In this process, the AgNPs act as self-propelled particles that are constantly removing silicon along their trajectories. High-resolution X-ray imaging and electron tomography reveal a resulting large open porosity and inner surface for potential applications in high-performance energy storage, harvesting and conversion or for on-chip sensorics and actuorics. Finally, the hierarchically porous silicon membranes can be transformed structure-conserving by thermal oxidation into hierarchically porous amorphous silica, a material that could be of particular interest for opto-fluidic and (bio-)photonic applications due to its multiscale artificial vascularization. Show Chinese abstract

Abstract: 许多生物材料表现出多尺度孔隙率，具有小的、主要是纳米级的孔以及大的宏观毛细管，以同时实现优化的质量传输能力和轻质结构以及大内表面积。 在人工材料中实现这种分层孔隙结构通常需要复杂且昂贵的自上而下加工方法，这限制了其可扩展性。 在这里，我们提出了一种方法，将基于金属辅助化学蚀刻（MACE）的自组织孔隙与光刻诱导的大孔隙相结合，用于合成具有双峰孔径分布的单晶硅，即直径为1微米的六边形排列圆柱形大孔，这些大孔由被60纳米中孔贯穿的壁隔开。 MACE过程主要由金属催化还原-氧化反应引导，其中银纳米颗粒（AgNPs）作为催化剂。 在这个过程中，AgNPs作为自推进粒子，沿着其轨迹不断去除硅。 高分辨率X射线成像和电子断层扫描揭示了 resulting 大的开放孔隙率和内表面，可用于高性能能量存储、收集和转换或芯片级传感器和执行器的潜在应用。 最后，分层多孔硅膜可以通过热氧化转化为结构保持的分层多孔非晶二氧化硅，这种材料由于其多尺度人工血管化，可能在光流体和（生物）光子应用中特别感兴趣。