Thickness measurement of amorphous SiO2 by EELS and electron holography

The accuracy of electron energy-loss spectroscopy (EELS) and electron holog raphy on thickness measurement of amorphous SiO2 was discussed. Since the S iO2 particles investigated in this work have a spherical shape, local thick ness along the incident electron beam can easily be evaluated. Thus, from E ELS, the mean free path of inelastic scattering was determined to be 178 +/ - 4nm at 200kV. It is considered that thickness measurement is limited to a morphous SiO2 film thicker than about 20 nm with EELS. On the other hand, f rom phase shift in the electron hologram, the mean inner potential was eval uated 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 po inted out that the accurate thickness measurement is possible for a thinner region with electron holography than EELS.