Direct Evidence for 1 nm Pores in “Dry” Thermal SiO2 from High Resolution Transmission Electron Microscopy

Thin films of thermally grown SiO2 have been studied by high resolution bright-field electron microscopy. Contrast phenomena observed in images from 9 nm thick “dry” films are consistent with the existence of 1 nm pores, typically 10 nm apart. Similar films grown in a wet oxidizing ambient do not display this contrast. A pore structure had previously been suggested to explain differences in growth behavior and electrical properties between “wet” and “dry” SiO2. The reliable detection of such pores or voids in electron micrographs from amorphous materials is not straightforward and a novel approach which has been successfully applied to these films is described. A simple model which explains the appearance of pores only in “dry” films is proposed and is related to the trapping behavior of thicker films. © 1980, The Electrochemical Society, Inc. All rights reserved.