Highly-antireflective porous Si films prepared with metal-assisted chemical etching

• The porous Si films were prepared using a facile wet etching process.
• The film thickness can be adjusted by the reaction durations.
• The average reflectivity of porous Si films can be significantly reduced to 0.5%.

Porous Si films were successfully prepared with a metal-assisted chemical etching (MaCE) process with isopropyl alcohol as solvents at room temperature. The as-prepared Si films on the p-type Si substrates exhibit a quite narrow distribution of pore size and the average dimension of nanopores is found to be 26.7 nm, following a typical Gaussian distribution. Investigations on etching rates, temperature-dependent kinetics and formation mechanism were performed. It is found that the thickness of porous films linearly increases with the etching time covering from 80 nm to 6.5 μm in thickness, demonstrating a sound controllability for the preparation of the porous Si layers. Furthermore, the reflectivity within visible spectrum of these porous films is found to be significantly reduced in comparison with the conventional alkaline-textured Si. By quantitatively comparing the antireflection behaviors of Si porous films synthesized upon various etching durations, the best antireflection capability of Si porous layers is prepared through 20-min MaCE reaction with average reflectance value of 0.5%.