Luminescence and structural properties of silicon-rich nitride by X-ray absorption spectroscopy

The luminescence and structural properties of silicon-rich nitride thin films were comprehensively examined by X-ray absorption spectroscopy. The near-edge X-ray absorption fine structures demonstrated the formation of silicon clusters in the silicon-rich nitride films. In addition, atomic resolved images of transmission electron microscope evidenced constitution of ultra-small (2–5 nm) silicon clusters. The X-ray absorption near-edge fine structures surveyed in photoluminescence yield and total electron yield configurations revealed that the luminescence are mainly coming from the Si–N bonding sites for lower degree of silicon-rich films. For higher silicon-rich samples, the Si–Si bonding sites increasingly contribute to the band edge absorption in the photoluminescence yield near-edge fine structures. These results strongly suggested that the transitions from the gap states localized in the surface of embedded silicon clusters and quantum confinement states within silicon clusters might contribute to the luminescence. The contribution weightiness of quantum confinement states increase while increasing the silicon-richness. It provides a reasonable explanation for the prolonged debates on the luminescence origins.