Band gap measurement by nano-beam STEM with small off-axis angle transmission electron energy loss spectroscopy (TEELS).

An energy band gap measurement method based on nano-beam STEM with small off-axis angle valence band transmission electron energy loss spectroscopy (TEELS) is reported. The effect of multiple scattering event is removed by self-convolution method to obtain a single scattering loss function and a dielectric function is calculated from the single scattering valence band energy loss function through Kramers-Kronig (K-K) analysis. Optical band gaps are extracted from energy loss spectra and the imaginary part of the dielectric functions for crystalline and amorphous SiOx, SiNx, and SiON through linear fitting of on-set regions yielding results that are independent of sample thickness. The TEELS band gap data are consistent with those obtained from reflection electron energy loss spectroscopy (REELS) measurements.