Fabrication of periodic, flexible and porous silicon microwire arrays with controlled diameter and spacing: Effects on optical properties

A new method of introducing nanopores with spongy morphology during fabrication of size and pitch controlled flexible silicon microwires (SiMWs) in wafer-scale is presented using nanosphere lithography technique in addition to metal catalyzed electroless etching technique by varying concentration of oxidant and introducing surfactant or co-solvents to the etching solution. For achieving a self-assembled monolayer closed-pack pattern of SiO₂ microparticles in wafer-scale simple spin coating process was used. The effect of variation of the etchant, oxidant, and surfactant on the morphology and optical properties of SiMWs were studied. By simply controlling the diameter of SiO₂ microparticles and concentration of H₂O₂ the size of the MWs as well as the introduction of pores could be controlled. The mechanism behind the formation of porous and flexible nature of the SiMWs is also demonstrated. Average reflectance was suppressed to below 8% in the broad spectral range of 400–800 nm for these SiMWs. The photoluminescence from the SiMWs showed a peak around 830 nm.