Synthesis and characterization of n-type lightly doped mesoporous silicon nanowires through 1-MACE, influence of etching solution temperature

Abstract

In this paper, large-area arrays of vertical and orderly mesoporous silicon nanowires (SiNWs) were fabricated through one-step metal assisted chemical etching (1-MACE) process using lightly doped n-Si substrate. Etching occurred in HF/ AgNO₃/ H₂O₂ solution. Field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) revealed that the whole surfaces of nanowires (NWs) are covered by dense mesoporous structures. Furthermore, the effect of solution etching temperature on morphological, optical and vibrational properties of SiNWs was investigated. FESEM images showed that the lengths of NWs are increased by increasing etching temperature, but the diameter changes are slight. Selected area electron diffraction (SAED) patterns indicate that the SiNWs formed at room temperature (RT) have single crystal structure, while those prepared at higher temperatures have polycrystal structure. In addition, the average reflectance is significantly low, i.e. less than 0.1% for SiNWs, in the wavelength range of 400–1100 nm. Also, a visible photoluminescence (PL) was observed in the samples, which is attributed to the silicon nano crystallites (SiNCs) decorated on the wall of NWs. The size of SiNCs is calculated through a frequency shift in the Raman spectrum. The optically active mesoporous SiNWs open new opportunities for nanoscale optoelectronic devices.