ALUMINA FILM SUBSTRATE AND ITS FABRICATION METHOD

摘要

An alumina film substrate has its surface that is so flat that an inspection of the surface by high-speed electron diffraction results in a banded pattern. A method for fabricating the alumina film substrate comprises a step for forming an epitaxial alumina film in such a way that after the surface of the substrate including aluminum is polished so as to be flattened, the substrate is heated in an oxygen atmosphere, thereby segregating the aluminum included in the substrate to the surface. There is provided a tunnel barrier material for forming a tunnel barrier layer having a uniform thin-film thickness, having an excellent breakdown resistance so that tunnel current is made to flow without causing a dielectric breakdown even if a voltage exceeding 5 × 10<SUP>9</SUP> V/m is applied, and not causing tunnel current fluctuations depending on the place. The tunnel barrier material can improve the operation efficiency, reliability, and lifetime, when it is applied to various elements using tunnel currents.