FTIR spectra and the percentage of Si = O symmetric stretching mode for the SROEr-I films. FTIR spectra of the SROEr-I films annealed at different temperatures. The spectrum of the as-deposited sample is denoted by empty squares, and that of the annealed samples are denoted by the colored lines. A typical fitting of the FTIR spectra is provided for the A.D. sample (the fitting data are denoted by dash-dot line). The sub-peaks A, B, and C represent the components from Si-O-Si bulk, Si-O-Si surface, and Si = O symmetric stretching modes, respectively. The inset shows the ratio of Si = O symmetric stretching mode for the SROEr-I films with different annealing temperatures.