RELATIVISTIC EFFECTS IN ELECTRON-ENERGY-LOSS-SPECTROSCOPY OBSERVATIONS OF THE SI SIO2 INTERFACE PLASMON PEAK/

Electron-energy-loss spectroscopy in a scanning transmission electron microscope has been used to study the interface plasmon peak (IPP) obs erved at the Si/SiO2 interface. A precise line-spectrum recording show s a shift of the interface plasmon peak from 7.8 to 6.8 eV from the in terface to 5 nm from it This shift is explained by considering relativ istic effects, demonstrating the importance of obtaining the relativis tic formulas given in the two appendixes. The agreement of the simulat ions with the experiment, both in position and intensity is very good and is improved further by the introduction of a 1.0-nm-thick intermed iate layer of SiO. A crystalline phase of SiO2 seems to be in poorer a greement with experiment. This implies that the careful recording and simulation of the IPP can actually give some information about the nat ure of interfaces.