The Formation of Porous Silicon Using Vertical Photoelectrochemical Method with Laser Energy Variation

Due to its notable characteristics, porous silicon (PSi) has become the main focus in silicon upgrades for optoelectronics, medical, and sensor applications. Here, successful vertical photoelectrochemical fabrication of PSi based on crystalline silicon n-type wafers with orientation (100) has been accomplished. Silicon surfaces were anodized for 10 min in a solution of hydrofluoric acid and ethanol at a ratio of 1:3 and a current density of 4 mA/cm 2 under laser illumination. Illumination sources were red, green, and purple laser beams with energies of 1.91 eV, 2.33 eV, and 3.06 eV, respectively, conducted to observe the effects on PSi microstructures and optical properties. The pores formed on the silicon surface were characterized via SEM, XRD, FTIR, and UV-Vis DRS Spectrophotometer. SEM analysis showed pore size distributions of 2.130, 3.353, and 1.078 mm for PSi samples with red, green, and purple lasers, respectively. XRD investigation revealed diffraction angles of 33.14° and 69.47° belonging to (211) and (422) planes, respectively, corresponding to the PSi. For samples of silicon and PSi with red, green, and purple lasers, the crystallite size and crystallinity were 168.55 nm and 44.80%, 25.02 nm and 17.12%, 29.19 nm and 23.56%, and 145.05 nm and 35.17%, respectively. FTIR observation confirmed that the PSi surface contained chemical bonds of Si-Si, Si-H, Si-H 2 , Si-O-Si, and C=O. UV-Vis DRS examination revealed the reflectance spectrum oscillation, indicating that lasers caused pore formation in PSi with bandgap energies of between 1 and 2 eV.