Epitaxial Insulating Films

Abstract

The study of insulating films is possible also with electrons, as soon as the charging up of the surface and the electron damage are avoided. Thin epitaxial films do not charge up, as long as the thickness is less than about 5 nm. Therefore the epitaxy of several insulating films could be studied using the spot profile analysis of low energy electron diffraction (SPA-LEED). The results show special features of growth, which are described as elastic bending of the growing films. For this phenomenon defects of the substrate or special growth conditions may be decisive. The features may be enhanced due to the strong binding within the ionic film compared to the weaker bonding to the substrate. Point defects are generated in NaCl films by electron bombardment with an energy over about 30 V. Since these defects have an electronic transition (color centers), they are easily quantitatively measured with electron energy loss spectroscopy. Therefore their effect on the background intensity of the elastic scattering has been studied quantitatively for the first time.