The high-resolution transmission-electron-microscopy (HRTEM) image of the ${\mathrm{SiO}}_2$/(001)Si interface varies with TEM specimen thickness. The most noticeable feature is the periodic image observed between the lattice fringe of the c-Si substrate and the granular image of ${\mathrm{SiO}}_2$ for the thick region of the specimen. Optical-diffraction-pattern observations clarified that each 111 spot obtained from the periodic image of the thick specimen is split into two spots. Simulation has revealed that both the periodic image and the 111 spot splitting are reproduced by interface roughness with Si protrusions delineated by {111} facets. The height of the Si protrusion can be evaluated by comparing the HRTEM images and the optical-diffraction pattern taken from the thick region of the specimen with simulated ones. For the interface formed by dry oxidation at 950 °C, the Si protrusion is higher than 6 monolayers.

• Received 17 August 1990

DOI:https://doi.org/10.1103/PhysRevB.44.1616