“…The absorption peaks of the silicon substrate spectrum, which are common to all samples, correspond to: (1) a Si-Si vibration mode in bulk c-Si at 611 cm -1 [20] (2) a Si-Si vibration mode in the presence of oxygen vacancy in SiO 2 at 669 cm -1 [21] (3) a two-phonon (LO + LA) Si mode at 738 cm -1 [22] (4) a bending Si-O-Si mode at 816 cm -1 [21], and ( 5), (6) a Si-O-Si asymmetric stretching doublet at 1074 and 1200 cm -1 , with the last two Si-O-Si modes involving mainly oxygen displacements [23]. The absorption peaks at (7) 2341 cm -1 and (8) 2360 cm -1 correspond to the P and R branch, respectively, of the asymmetric stretching mode of CO 2 gas, present in the atmosphere when taking the IR transmittance measurements [24].…”