Tohoku University · Materials Science
Professor Yuji Matsumoto's research lab specializes in the development and characterization of advanced oxide semiconductors and functional thin films, with a focus on transparent ferromagnetic oxides, epitaxial oxide heterostructures, and complex oxide thin films for spintronic and electronic device applications. The lab employs advanced epitaxial growth techniques such as laser molecular beam epitaxy (Laser MBE) and combinatorial synthesis to achieve atomic-level control over film composition, structure, and interface properties. Key research directions include band gap engineering in ZnO-based oxides, flux-mediated epitaxy for bismuth-based ferroelectrics, and the growth of magnetic semiconductors like Co-doped TiO₂ with long-range ferromagnetic order. The lab also leverages advanced characterization tools like scanning SQUID microscopy and STM to probe magnetic and electronic nanostructures at the atomic scale.
Figures are computed from collected data and may differ slightly.
Dilute magnetic semiconductors and wide gap oxide semiconductors are appealing materials for magnetooptical devices. From a combinatorial screening approach looking at the solid solubility of transition metals in titanium dioxides and of their magnetic properties, we report on the observation of transparent ferromagnetism in cobalt-doped anatase thin films with theconcentration of cobalt between 0 and 8%. Magnetic microscopy images reveal a magnetic domain structure in the films, indicating the
Epitaxial TiO 2 rutile films were fabricated on α-Al 2 O 3 (1012) substrate in the layer-by-layer fashion by laser molecular beam epitaxy. Ablation with a Co-doped TiO 2 target produced single phase of rutile film with the concentration of Co between 0 and 5%. Some ferromagnetic domain structures were observed in Co x Ti 1- x O 2 rutile films by a scanning superconducting quantum interference device microscope at 3 to 90 K. The magnetic hysteresis could also be observed even at room temperature
We have developed a new combinatorial synthesis system integrating a combinatorial shadow mask into a laser MBE (molecular beam epitaxy) chamber. This combinatorial Laser MBE system can be used for fabricating a number of crystalline films with different compositions on a substrate under programmed temperature and pressure conditions. The method was applied to alloying and band gap engineering of ZnO by positional substitution of Mg into ZnO thin films. The superiority of the combinatorial metho
Abstract Excellent crystallinity of material films and atomic control of their surface/interface, sufficient for the realization of their optimal physical properties, are technological premises for modern functional‐device applications. Bi 4 Ti 3 O 12 and related compounds attract much interest as highly insulating, ferroelectric materials for use in ferroelectric random‐access memories. However, it has been difficult thus far for Bi 4 Ti 3 O 12 films to satisfy such requirements when formed usi
Growth of Ni on a c (2×2)-N Cu(100) surface was studied by scanning tunneling microscopy (STM). When Ni atoms are vaporized on a Cu(100) surface with square c (2×2)-N patches, one-atomic-layer Ni islands with an average size of 50 Å are grown on the virgin area remaining at the corner of c (2×2)-N patches, so that uniform-size Ni islands are arranged like a checkerboard. This checkerboard arrangement of Ni islands is stable up to 470 K. Stronger interaction of the Ni layer with the clean area co
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