Surface x-ray-absorption fine structures of ${\mathrm{SiO}}_{\mathit{x}}$ (0<x<2) and ${\mathrm{SiN}}_{\mathit{x}}$ (0<x<4/3) produced by low-energy ion implantation in Si(100)

X-ray-absorption near-edge structures (XANES) have been investigated for silicon oxide and nitride with nonstoichiometric compositions (${\mathrm{SiO}}_{\mathit{x}}$, ${\mathrm{SiN}}_{\mathit{x}}$) produced by low-energy ion implantation in Si(100). The XANES structures at the Si 2p edge for ${\mathrm{SiO}}_{\mathit{x}}$ at x≥0.2 resemble those reported for ${\mathrm{SiO}}_2$, and those at the O 1s edge are independent of the x value. These observations indicate that the conduction band of ${\mathrm{SiO}}_{\mathit{x}}$ is mainly composed of the orbitals of ${\mathrm{SiO}}_2$. On the other hand, the XANES structures of ${\mathrm{SiN}}_{\mathit{x}}$ change with the x value, and the sharp resonance corresponding to a N dangling bond was observed at the N 1s edge for x>1.0. These findings suggest that in the ${\mathrm{SiN}}_{\mathit{x}}$ phase there is a random-bonding structure rather than a mixture of Si and ${\mathrm{Si}}_3$ ${\mathrm{N}}_4$ islands.