Thickness Measurement of Amorphous SiO<SUB>2</SUB> by EELS and Electron Holography

Abstract

The accuracy of electron energy-loss spectroscopy (EELS) and electron holography on thickness measurement of amorphous SiO 2 was discussed. Since the SiO 2 particles investigated in this work have a spherical shape, local thickness along the incident electron beam can easily be evaluated. Thus, from EELS, the mean free path of inelastic scattering was determined to be 178 ± 4nm at 200kV. It is considered that thickness measurement is limited to amorphous SiO 2 film thicker than about 20 nm with EELS. On the other hand, from phase shift in the electron hologram, the mean inner potential was evaluated to be 11.5 ± 0.3 V. It is suggested that the thickness measurement is possible up to a few nanometers with electron holography. Thus, it is pointed out that the accurate thickness measurement is possible for a thinner region wilt electron holography than EELS.