Jun Kuwata

Interaction of reactively sputtered TaOx thin films with In‐Sn‐O thin films and properties of TaOx thin films

The interaction of reactively sputtered TaOx films with In‐Sn‐O (ITO) films was investigated. Phenomena observed in the TaOx/ITO layer structure after a postannealing were studied. These phenomena were: a rise in electrical resistance of the ITO films and a change in color of the layer from transparent to yellowish. Monitoring the gases evolved from the TaOx films during the heating under vacuum showed that incorporation of water into the TaOx films takes place. Evolution of this water from the TaOx films started at around 350 °C, peaked at around 500 °C, and was largely complete at around 650 °C. It was found that the occurrence of the phenomena described above appeared at precisely the temperature at which water was evolved from the TaOx films. It was concluded that the water component incorporated into the TaOx films was the origin of both phenomena. Water present in the conditions under which discharge deposition takes place would be the cause of that incorporation.

Thermally stable exchange-biased magnetic tunnel junctions over 400 °C

Exchange-biased magnetic tunnel junctions (MTJs) with interposed Fe1−xPtx metal alloy layers between the Al oxide barrier and the ferromagnetic electrodes maintain large tunneling magnetoresistance (TMR) after thermal treatment in excess of 400 °C, owing to an improved barrier interface. After 400 °C annealing, TMRs of MTJs with Fe1−xPtx (x=0.1–0.2) exhibit over 40% and retain 30% TMR after 420 °C annealing. The tunnel barrier height derived from the current–voltage curve fitted to the Simmons equation increases with richer Pt content. Secondary ion mass spectroscopy depth profiles and cross-section transmission electron micrographs of MTJs with Fe0.85Pt0.15 show a clear interface around the Al oxide barrier even after annealing at 400 °C.

Concentration profiles of composing ions in radio frequency sputtered Sr (Zr0.2Ti0.8)O3 films

Sr(Zr0.2 Ti0.8 )O3 dielectric thin film for electroluminescent devices was prepared by in‐line‐type rf magnetron sputtering method using oxide target. Novel phenomenon of periodic concentration fluctuations of the composing ions was observed in SIMS in‐depth profiles. Partial concentration anomaly with Sr deficiency was also observed in the first‐to‐grow region of the film. The periodic concentration fluctuations were confirmed to be ascribed to periodic appearance of Sr(Zr1−x Tix )O3 with x larger than 0.8.