Combined optical, surface and nuclear microscopic assessment of porous silicon formed in HF-acetonitrile

A new type of HF solution, HF-acetonitrile (MeCN), has been employed to produce 10-30 μm thick porous silicon (P-Si) layers by photoelectrochemical etching of different types of Si wafers, Si(100), Si(111) and polycrystalline Si, with different resistivities. A combined optical, surface and nuclear microscopic assessment of these P-Si layers was performed using photoluminescence (PL), Raman scattering, X-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy. With increasing resistivity of the Si(100) wafers, the P-Si layers show a slight blue shift of their visible light emission peak energy, an up shift of the peak position and a narrowing of the band width of the dominant Raman band, and a decrease in the amount of residual elemental Si on the surface. Those Si(111) wafers, etched in HF-MeCN, showed no porous structures and no visible light emission.