Infrared spectra of silicon nanowires

Infrared (IR) spectra of the silicon nanowires (SiNWs) with oxide layer are analyzed by introducing the disorder-induced mechanical coupling between the optically active oxygen asymmetric stretch (AS) and inactive oxygen asymmetric stretch (I-AS) modes in terms of the transverse-optic (TO) and longitudinal-optic (LO) vibrational modes. The shapes of the IR spectra are similar to that of the reported SiO2, indicating that the SiNWs possess an oxide layer outside. The TO frequencies of coupled AS and I-AS are experimentally observed as peak at approximately 1085 cm− 1 and its shoulder of 1200 cm− 1, respectively. The other TO absorption peaks of ∼ 468 cm− 1, ∼ 480 cm− 1, and ∼ 808 cm− 1 are also observed. Furthermore, the intensity of the AS-mode TO band centered at ∼ 1085 cm− 1 decreases while those of silicon lattice absorption peaks are enhanced with the crystalline quality increased.