Photoluminescence of silanone and dioxasilyrane groups in silicon oxides: A theoretical study

Abstract

The photoluminescence (PL) properties of silanone, =Si=O, and dioxasilyrane, =Si(O2), in substoichiometric silicon oxide layers have been investigated by high-level ab initio calculations. The calculated 2.3 and 1.6 eV PL energies are evidenced to correspond to transitions from two lowest excited singlet states in silanone. Additional broadening of the PL bands is due to an involvement of the ground-state =Si=O stretching and bending vibrations with frequencies of ∼1300 and ∼360 cm−1, respectively. As dioxasilyrane group is excited to the S2 (21A1) states, five excited states 11B2, 21A1, 11A2, 31A1, and 11B1 are involved in radiationless and radiative relaxation. The excitation initiates a rupture of the O–O bond and the deexcitation process drives through the activation of O–O stretching vibrations in the ground state (∼630 cm−1). The radiative 31A1→11A1 transition contributes to PL in the range from 2.05 to 2.3 eV, while the 31A1→11B2 and 11B1→11A1 transitions can produce PL bands at 1.7–1.8 eV. The calculated results are compared with green PL bands experimentally observed for a wide range of nanoscale silicon and silicon oxide materials.