Author
Makoto Murakami
Other affiliations: Tokyo Institute of Technology
Bio: Makoto Murakami is an academic researcher from University of Maryland, College Park. The author has contributed to research in topics: Thin film & Pulsed laser deposition. The author has an hindex of 24, co-authored 50 publications receiving 4976 citations. Previous affiliations of Makoto Murakami include Tokyo Institute of Technology.
Papers
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TL;DR: The observation of transparent ferromagnetism in cobalt-doped anatase thin films with the concentration of cobalt between 0 and 8% is reported, indicating the existence of ferromagnetic long-range ordering.
Abstract: 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 the concentration of cobalt between 0 and 8%. Magnetic microscopy images reveal a magnetic domain structure in the films, indicating the existence of ferromagnetic long-range ordering. The materials remain ferromagnetic above room temperature with a magnetic moment of 0.32 Bohr magnetons per cobalt atom. The film is conductive and exhibits a positive magnetoresistance of 60% at 2 kelvin.
2,302 citations
TL;DR: Combinatorial laser molecular-beam epitaxy method was employed to fabricate epitaxial ZnO thin films doped with all the 3d transition metal (TM) ions in a high throughput fashion as discussed by the authors.
Abstract: Combinatorial laser molecular-beam epitaxy method was employed to fabricate epitaxial ZnO thin films doped with all the 3d transition metal (TM) ions in a high throughput fashion The solubility behavior of TM ions was discussed from the viewpoints of the ionic radius and valence state The magneto-optical responses coincident with absorption spectra were observed for Mn- and Co-doped samples Cathodoluminescence spectra were studied for Cr-, Mn-, Fe-, and Co-doped samples, among which Cr-doped ZnO showed two sharp peaks at 297 eV and 371 eV, respectively, at the expense of the exciton emission peak of pure ZnO at 325 eV Different magnetoresistance behavior was observed for the samples codoped with n-type carriers Ferromagnetism was not observed for Cr- to Cu-doped samples down to 3 K
587 citations
TL;DR: In this paper, a lead-free morphotropic phase boundary was discovered in Sm doped BiFeO3 with a simple perovskite structure using the combinatorial thin film strategy.
Abstract: We report on the discovery of a lead-free morphotropic phase boundary in Sm doped BiFeO3 with a simple perovskite structure using the combinatorial thin film strategy. The boundary is a rhombohedral to pseudo-orthorhombic structural transition which exhibits a ferroelectric (FE) to antiferroelectric (AFE) transition at approximately Bi0.86Sm0.14FeO3 with dielectric constant and out-of-plane piezoelectric coefficient comparable to those of epitaxial (001) oriented Pb(Zr,Ti)O3 (PZT) thin films at the MPB. The discovered composition may be a strong candidate of a Pb-free piezoelectric replacement of PZT.
250 citations
TL;DR: In this article, a lead-free morphotropic phase boundary (MPB) was discovered in Sm doped BiFeO3 with a simple perovskite structure using the combinatorial thin film strategy.
Abstract: We report on the discovery of a lead-free morphotropic phase boundary (MPB) in Sm doped BiFeO3 with a simple perovskite structure using the combinatorial thin film strategy. The boundary is a rhombohedral to pseudo-orthorhombic structural transition which exhibits a ferroelectric to antiferroelectric transition at approximately Bi0.86Sm0.14FeO3 with dielectric constant and out-of-plane piezoelectric coefficient comparable to those of epitaxial (001) oriented PbZr0.52Ti0.48O3 (PZT) thin films at the MPB. The discovered composition may be a strong candidate of a Pb-free piezoelectric replacement of PZT.
239 citations
TL;DR: In this paper, a new combinatorial synthesis system integrating a shadow mask into a laser MBE chamber was developed for fabricating a number of crystalline films with different compositions under programmed temperature and pressure conditions.
Abstract: 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 methodology to conventional one-by-one synthesis is evident from the high linearity of the c-axis length and band gap dependence on Mg content.
180 citations
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TL;DR: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature.
Abstract: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...
10,260 citations
TL;DR: This review describes a new paradigm of electronics based on the spin degree of freedom of the electron, which has the potential advantages of nonvolatility, increased data processing speed, decreased electric power consumption, and increased integration densities compared with conventional semiconductor devices.
Abstract: This review describes a new paradigm of electronics based on the spin degree of freedom of the electron. Either adding the spin degree of freedom to conventional charge-based electronic devices or using the spin alone has the potential advantages of nonvolatility, increased data processing speed, decreased electric power consumption, and increased integration densities compared with conventional semiconductor devices. To successfully incorporate spins into existing semiconductor technology, one has to resolve technical issues such as efficient injection, transport, control and manipulation, and detection of spin polarization as well as spin-polarized currents. Recent advances in new materials engineering hold the promise of realizing spintronic devices in the near future. We review the current state of the spin-based devices, efforts in new materials fabrication, issues in spin transport, and optical spin manipulation.
9,917 citations
TL;DR: Titanium dioxide is the most investigated single-crystalline system in the surface science of metal oxides, and the literature on rutile (1.1) and anatase surfaces is reviewed in this paper.
7,056 citations
TL;DR: This paper presents a meta-analyses of the chiral stationary phase transition of Na6(CO3)(SO4)2, Na2SO4, and Na2CO3 of the Na2O/Na2O 2 mixture at the stationary phase and shows clear patterns in the response of these two materials to each other.
Abstract: Jenny Schneider,*,† Masaya Matsuoka,‡ Masato Takeuchi,‡ Jinlong Zhang, Yu Horiuchi,‡ Masakazu Anpo,‡ and Detlef W. Bahnemann*,† †Institut fur Technische Chemie, Leibniz Universitaẗ Hannover, Callinstrasse 3, D-30167 Hannover, Germany ‡Faculty of Engineering, Osaka Prefecture University, 1 Gakuen-cho, Sakai Osaka 599-8531, Japan Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, China
4,353 citations
TL;DR: In this paper, photo-induced superhydrophilicity was used on the surface of a wide-band gap semiconductor like titanium dioxide (TiO 2 ) for photocatalytic activity towards environmentally hazardous compounds.
4,241 citations