Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session A3b: Superconductivity in Diamond |
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Sponsoring Units: DCMP Chair: Joe Thompson, LANL Room: LACC 515B |
Monday, March 21, 2005 9:48AM - 10:24AM |
A3b.00001: Superconductivity in Bulk, Hole-Doped Diamond Invited Speaker: Diamonds, synthesized at high pressure (9 GPa) and high temperature (2500-2800 K) in the systems boron carbide-graphite and boron-graphite, are heavily hole-doped by incorporation of boron into the diamond lattice. These diamonds were characterized by: X-ray diffraction, Raman scattering, NMR, SQUID magnetometry, calorimetry, Hall effect, resistivity and magnetic susceptibility measurements. They show an expanded ($\sim $1 {\%} in volume) lattice with a softened zone-centre optical phonon mode and reduced Debye temperature, and exhibit bulk superconductivity below Tc $\sim $4 K. Upper critical field, specific heat and resistivity measurements provide a consistent set of materials parameters that favor a conventional, weak coupling electron-phonon interpretation of the superconducting mechanism at high hole doping. Preliminary measurements of conductance spectra, obtained with contacts fabricated at the surface of these hole-doped diamonds, indicate the appearance of superconducting gap below Tc. [Preview Abstract] |
Monday, March 21, 2005 10:24AM - 11:00AM |
A3b.00002: Superconductivity in CVD Diamond Films Invited Speaker: The recent news of superconductivity 2.3K in heavily boron-doped diamond synthesized by high pressure sintering was received with considerable surprise (1). Opening up new possibilities for diamond-based electrical devices, a systematic investigation of these phenomena clearly needs to be achieved. Application of diamond to actual devices requires it to be made into the form of wafers or thin films. We show unambiguous evidence for superconductivity in a heavily boron-doped diamond thin film deposited by the microwave plasma assisted chemical vapor deposition (MPCVD) method (2). An advantage of the MPCVD deposited diamond is that it can control boron concentration in its wider range, particularly in (111) oriented films. The temperature dependence of resistivity for (111) and (100) homoepitaxial thin films were measured under several magnetic fields. Superconducting transition temperatures of (111) homoepitaxial film are determined to be 11.4K for Tc onset and 7.2K for zero resistivity. And the upper critical field is estimated to be about 8T. These values are 2-3 times higher than these ever reported (1,3). On other hand, for (100) homoepitaxial film, Tc onset and Tc zero resistivity were estimated to be 6.3 and 3.2K respectively. The superconductivity in (100) film was strongly suppressed even at the same boron concentration. These differences of superconductivity in film orientation will be discussed. These findings established the superconductivity as a universal property of boron-doped diamond, demonstrating that device application is indeed a feasible challenge. 1. E. A. Ekimov et al. Nature, 428, 542 (2004). 2. Y. Takano et al., Appl. Phys. Lett. 85, 2851 (2004). 3. E. Bustarret et al., ond-mat 0408517. [Preview Abstract] |
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