Porous Silicon Dioxide Synthesized using Photoelectrochemical (PEC) Wet Etching

Porous SiO₂ can be used as a template to reduce substrate-induced stress, similar to porous GaN. Such a regrowth method may reduce the defect density in the epitaxial layer leading to high quality stress free layer on porous template. The samples were prepared on silicon (Si) wafers, (111)-oriented, with n- doping. After standard cleaning steps, SiO₂ of 1200 Aring thickness was prepared by thermal oxidation of the Si at 1000deg C for 1.50 hours. The wafer was then cleaved into few pieces. To prepare porous structures by photoelectrochemical (PEC) method, the samples were dipped into a mixture of hydrofluoric acid (HF): water: ethanol under different etching durations. Structural properties of porous SiO₂ have been investigated by scanning electron microscope (SEM). Elemental composition of the sample was identified using energy dispersive X-ray (EDX) analysis. Fourier transform infrared reflectance (FTIR) spectroscopy was used to characterize the chemical species and chemical bonding state.