Rajkumar Kanakaraj, Pandian Ramanathaswamy, Sankarakumar Amirthapandian, Rajendra Kumar Ramasamy Thangavelu
Department of Physics, Advanced Materials and Devices Laboratory (AMDL), Department of Nanoscience and Technology, and DRDO-BU-CLS, Bharathiar University, Coimbatore, Tamil Nadu 641046, India.
Materials Science Group, Indira Gandhi Center for Atomic Research, Kalpakkam, Tamil Nadu 603102, India.
ACS Omega. 2017 Aug 15;2(8):4540-4547. doi: 10.1021/acsomega.7b00584. eCollection 2017 Aug 31.
We demonstrate controlled fabrication of porous Si (PS) and vertically aligned silicon nanowires array starting from bulk silicon wafer by simple chemical etching method, and the underlying mechanism of nanostructure formation is presented. Silicon-oxidation rate and the electron-scavenging rate from metal catalysis play a vital role in determining the morphology of Si nanostructures. The size of Ag catalyst is found to influence the Si oxidation rate. Tunable morphologies from irregular porous to regular nanowire structure could be tailored by controlling the size of Ag nanoparticles and HO concentration. Ag nanoparticles of size around 30 nm resulted in irregular porous structures, whereas discontinuous Ag film yielded nanowire structures. The depth of the porous Si structures and the aspect ratio of Si nanowires depend on HO concentration. For a fixed etching time, the depth of the porous structures increases on increasing the HO concentration. By varying the HO concentration, the surface porosity and aspect ratio of the nanowires were controlled. Controlling the Ag catalyst size critically affects the morphology of the etched Si nanostructures. HO concentration decides the degree of porosity of porous silicon, dimensions and surface porosity of silicon nanowires, and etch depth. The mechanisms of the size- and HO-concentration-dependent dissociation of Ag and the formation of porous silicon and silicon nanowire are described in detail.
我们展示了从体硅晶圆出发，通过简单化学蚀刻方法可控制备多孔硅（PS）和垂直排列的硅纳米线阵列，并阐述了纳米结构形成的潜在机制。硅的氧化速率和金属催化的电子清除速率在决定硅纳米结构的形态方面起着至关重要的作用。发现银催化剂的尺寸会影响硅的氧化速率。通过控制银纳米颗粒的尺寸和过氧化氢（HO）浓度，可以定制从不规则多孔到规则纳米线结构的可调形态。尺寸约为30 nm的银纳米颗粒会产生不规则的多孔结构，而不连续的银膜则会产生纳米线结构。多孔硅结构的深度和硅纳米线的纵横比取决于过氧化氢浓度。对于固定的蚀刻时间，多孔结构的深度会随着过氧化氢浓度的增加而增加。通过改变过氧化氢浓度，可以控制纳米线的表面孔隙率和纵横比。控制银催化剂的尺寸对蚀刻后的硅纳米结构的形态有至关重要的影响。过氧化氢浓度决定了多孔硅的孔隙率程度、硅纳米线的尺寸和表面孔隙率以及蚀刻深度。详细描述了银的尺寸和过氧化氢浓度依赖性解离以及多孔硅和硅纳米线形成的机制。
