Aluminum Oxide Films Prepared by Electron Beam Evaporation of Sapphire

Abstract

Insulating films of aluminum oxide are made by electron beam evaporation of sapphire. Both the values of the loss tangent and the dielectric constant are measured against frequency by using the materials of Al–Al2O3–Al sandwich structure. The values of loss tangent are 0.006 for this films at 103Hz and the value of their dielectric constant at 106Hz is 2 per cent lower than that at 103Hz. The structures of films are determined by electron microscopy and transmission electron diffraction and the correlation between the structure and the values of loss tangent are also obtained. The evaporation parameters such as the deposition rate and the composition of residual gas under evaporation, are discussed about the electrical properties of aluminum oxide films. The results of the preliminary application to MOS diode such as Al–Al2O3–Si and Al–Al2O3–CdS structures are also presented.