Influence of thermal annealing on oxidation states of Al-oxide in spin tunneling junctions

• Published in: Journal of magnetism and magnetic materials Vol. 303; no. 1; pp. 256 - 260
• Main Authors: Kaiju, Hideo, Otaka, Yuki, Shiiki, Kazuo
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.08.2006; Elsevier Science
• Subjects: Al-oxide; Annealing; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dielectric constant; Dielectric properties of solids and liquids; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Exact sciences and technology; Ion-beam sputtering; Permittivity (dielectric function); Physics; Spin tunneling junctions; Ion-beam sputtering; 77.55.+f; 75.80.Pa; Dielectric constant; Annealing; 73.40.Gk; Al-oxide; Spin tunneling junctions; Ion beam sputtering; 75.80.Pa Spin tunneling junctions; Chemical composition; Tunnel junction; Oxidation; Thermal annealing; Permittivity; Aluminium oxides; X-ray photoelectron spectra
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2005.11.017

The dielectric constant in annealing coercive differential spin tunneling junctions Co/Al-oxide/Co has been investigated in order to clear the influence of thermal annealing on oxidation states. Al oxidized naturally in pure O 2 shows the relative dielectric constant of 10–40 before annealing. It indicates that Al oxidized in pure O 2 can be AlO 2 because the dielectric constant of AlO 2 is approximately 22.7. This dielectric measurement result is in good agreement with XPS analysis results that O/Al ratio is 1.9–2.0. After annealing at temperature ranging from room temperature up to 250 °C, the relative dielectric constant approaches approximately 8.0, which is equal to that of Al 2O 3. This indicates that the phase of Al-oxide is changing from AlO 2 to Al 2O 3 by annealing. This dielectric measurement will help investigate the oxidation state, such as chemical composition for junctions themselves.