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5 Aug 2002

Volume 81, Issue 6, pp. 951-1149

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Investigation of the energy band structure of orthorhombic BaSi2 by optical and electrical measurements and theoretical calculations

Tomoyuki Nakamura, Takashi Suemasu, Ken-ichiro Takakura, Fumio Hasegawa, Akihiro Wakahara, and Motoharu Imai

Appl. Phys. Lett. 81, 1032 (2002); http://dx.doi.org/10.1063/1.1498865 (3 pages) | Cited 25 times

Online Publication Date: 30 July 2002

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Optical and electrical properties of polycrystalline orthorhombic BaSi2 prepared by arc melting in Ar atmosphere were investigated. The optical absorption spectra measured at room temperature showed that indirect and direct absorption edges were 1.15 and 1.25 eV, respectively. The activation energy estimated from temperature dependence of the resistivity was 1.10 eV. These results agreed well with a calculated band structure of the orthorhombic BaSi2 by first principles calculation using density functional theory. © 2002 American Institute of Physics.
Show PACS
71.20.Nr Semiconductor compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
78.66.Li Other semiconductors
73.61.Le Other inorganic semiconductors
78.40.Fy Semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Epitaxial MgO layer for low-resistance and coupling-free magnetic tunnel junctions

E. Popova, J. Faure-Vincent, C. Tiusan, C. Bellouard, H. Fischer, M. Hehn, F. Montaigne, M. Alnot, S. Andrieu, A. Schuhl, E. Snoeck, and V. da Costa

Appl. Phys. Lett. 81, 1035 (2002); http://dx.doi.org/10.1063/1.1498153 (3 pages) | Cited 32 times

Online Publication Date: 30 July 2002

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Epitaxially grown magnetic tunnel junctions MgO(100)/Fe/MgO/Fe/Co/Pd have been elaborated by molecular beam epitaxy, with insulating layer thickness down to 0.8 nm. The continuity of this layer was checked at different spatial scales by means of morphological (high resolution transmission electronic microscopy), electric (local impedance), and magnetic (magnetoresistance and hysteresis loop) measurements. These junctions show a low resistance (4 kΩ μm2), tunnel magnetoresistance up to 17%, and a very small interlayer magnetic coupling. © 2002 American Institute of Physics.
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75.47.De Giant magnetoresistance
73.40.Gk Tunneling
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.Ac Multilayers
75.50.Bb Fe and its alloys
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
72.15.Gd Galvanomagnetic and other magnetotransport effects
68.35.Ct Interface structure and roughness
68.37.Lp Transmission electron microscopy (TEM)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Achieving highly conductive AlGaN alloys with high Al contents

K. B. Nam, J. Li, M. L. Nakarmi, J. Y. Lin, and H. X. Jiang

Appl. Phys. Lett. 81, 1038 (2002); http://dx.doi.org/10.1063/1.1492316 (3 pages) | Cited 23 times

Online Publication Date: 30 July 2002

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Si-doped n-type AlxGa1−xN alloys were grown by metalorganic chemical vapor deposition on sapphire substrates. We have achieved highly conductive n-type AlxGa1−xN alloys for x up to 0.7. A conductivity (resistivity) value of 6.7 Ω−1 cm−1 (0.15 Ω cm) (with free electron concentration 2.1×1018 cm−3 and mobility of 20 cm2/Vs at room temperature) has been achieved for Al0.65Ga0.35N, as confirmed by Hall-effect measurements. Our experimental results also revealed that (i) the conductivity of AlxGa1−xN alloys continuously increases with an increase of Si doping level for a fixed value of Al content and (ii) there exists a critical Si-dopant concentration of about 1×1018 cm−3 that is needed to convert insulating AlxGa1−xN with high Al content (x ≥ 0.4) to n-type. © 2002 American Institute of Physics.
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73.61.Ey III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.20.Fr Low-field transport and mobility; piezoresistance
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