STM/STS study of superconducting diamond

Ekimov, Evgeny A.; Sidorov, V. A.; Rakhmanina, A. V.; Melnik, N. N.; Садыков, Р. А.; Thompson, J. D.

doi:10.1016/j.stam.2006.03.004

Cited by 16 publications

(11 citation statements)

References 24 publications

(13 reference statements)

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“…We have checked that tunneling spectra did not depend on the tunnel resistance set point in the range 1 -10 M⍀. In contrast to early STM measurements on similar samples, 20,21 we observe in many locations an almost fully opened gap, presumably thanks to a better sample surface morphology. Within one grain, the electronic properties change smoothly as expected for a slow variation in doping concentration ͑small Fig.…”

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confidence: 99%

Spatially correlated microstructure and superconductivity in polycrystalline boron-doped diamond

et al. 2010

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Scanning tunneling spectroscopies are performed below 100 mK on polycrystalline boron-doped diamond films characterized by transmission electron microscopy and transport measurements. We demonstrate a strong correlation between the local superconductivity strength and the granular structure of the films. The study of the spectral shape, amplitude, and temperature dependence of the superconductivity gap enables us to differentiate intrinsically superconducting grains that follow the BCS model, from grains showing a different behavior involving the superconducting proximity effect. DOI: 10.1103/PhysRevB.82.033306 PACS number͑s͒: 73.22.Ϫf, 73.61.Cw, 74.45.ϩc, 74.81.Bd Over the last few years, superconductivity has been discovered in heavily doped group IV covalent semiconductors, 1 in particular, diamond 2 and silicon. 3 In the case of diamond, low-temperature superconductivity appears at the same doping level than the metallic state created by heavy boron doping. 4 Evidence for a pairing mechanism mediated by phonons in the weak-coupling limit has been provided among others by very low-temperature scanning tunneling spectroscopy of single-crystal epilayers. 5Polycrystalline diamond films can be a new model system for the general issue of the nature of superconductivity in strongly disordered metals. 6 In such systems, disorder sits either at the atomic scale, in which case electronic excitations can become localized so that superconductivity vanishes 7 or at a larger scale, for instance, that of a granular structure, in which case the two competing mechanisms are the Coulomb blockade and the superconducting proximity effect. 8,9 Nevertheless, recent studies of polycrystalline diamond films 10,11 did not provide a clear picture on the coexistence between superconductivity and disorder in these films.In this Brief Report, we report a study of the local superconducting and structural properties of high-quality polycrystalline boron-doped diamond by very low-temperature scanning tunneling microscopy ͑STM͒. The granular structure was consistently characterized by STM and transmission electron microscopy ͑TEM͒. In contrast with epitaxial films, a strong correlation is observed between the granular microstructure and the superconductivity local strength. The spatial evolution and temperature dependence of the local electronic density of states are consistent with the picture of an assembly of grains, which either follow the BCS model or present another superconducting behavior involving the superconducting proximity effect.Boron-doped polycrystalline diamond thin films of different thicknesses were grown as described elsewhere 12,13 by microwave plasma-enhanced chemical-vapor deposition from hydrogen-rich methane-trimethylborane-hydrogen gaseous mixtures on ultrasonically seeded quartz ͑sample A͒ and oxidized silicon ͑sample B͒ substrates. As shown by Figs. 1͑a͒ and 1͑b͒ displaying, respectively, a very lowtemperature STM ͑Refs. 14 and 15͒ topography of sample A and a TEM cross section in bright-field condition of sa...

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Spatially correlated microstructure and superconductivity in polycrystalline boron-doped diamond

et al. 2010

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“…We observed similar behavior for other pressure-synthesized samples. A superconducting energy gap was observed in diamond by means of STM in pressure-synthesized samples by Troyanovsky et al [9] and in single-crystalline CVD films by Sace´pe et al [10]. The latter authors were able to observe a triangular Abrikosov vortex lattice and to find a precise temperature dependence of the energy gap in the superconducting state of B-doped diamond.…”

Section: Resultsmentioning

confidence: 99%

Superconducting and normal state properties of heavily hole-doped diamond synthesized at high pressure

Nakagawa

Tokunaga

Tamegai

2006

Science and Technology of Advanced Materials

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Diamonds, synthesized at high pressures and high temperatures in the presence of boron, are heavily hole-doped by incorporation of boron into the diamond lattice. These diamonds become superconducting below T c ¼ 2-9 K. Synthesis in the systems B-C and B 4 C-C at P ¼ 9 GPa and T ¼ 2500-2800 K result in formation of polycrystalline carbonado-like material, whereas synthesis from B-C-H gives small single crystals and intergrowth plates. Dense superconducting bodies can be prepared by compacting these single crystal particles at P ¼ 8 GPa and T ¼ 1800 K. Specific heat and resistivity measurements in magnetic fields prove the bulk nature of superconductivity in all pressure-synthesized samples and provide a consistent set of materials parameters that favor a conventional weak-coupling electron-phonon interpretation of the superconducting mechanism at high hole doping. Schottky barrier tunneling conductance spectra, obtained with contacts fabricated at the surface of these hole-doped diamonds, indicate the appearance of superconducting gap below T c .

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“…Here we can also invoke some kind of Anderson's theorem and suggest that randomness gets renormalized to small values when we consider pairing among time-reversed states rather than Bloch states. The scanning tunnelling microscopy in superconducting boron doped diamond [26,27] does show strong spatial inhomogeneity in the order parameter, and at the same time, the system exhibits a robust bulk superconductivity. It has been suggested that the (singlet) valence bond maximization [28] holds the key to superconductivity.…”

Section: Mott Insulating Quantum Spin Liquid To a Superconductor Tranmentioning

confidence: 99%

Impurity band Mott insulators: a new route to highT_csuperconductivity

Baskaran

2008

Science and Technology of Advanced Materials

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Last century witnessed the birth of semiconductor electronics and nanotechnology. The physics behind these revolutionary developments is certain quantum mechanical behaviour of 'impurity state electrons' in crystalline 'band insulators', such as Si, Ge, GaAs and GaN, arising from intentionally added (doped) impurities. The present article proposes that certain collective quantum behaviour of these impurity state electrons, arising from Coulomb repulsions, could lead to superconductivity in a parent band insulator, in a way not suspected before. Impurity band resonating valence bond theory of superconductivity in boron doped diamond, recently proposed by us, suggests possibility of superconductivity emerging from impurity band Mott insulators. We use certain key ideas and insights from the field of high-temperature superconductivity in cuprates and organics. Our suggestion also offers new possibilities in the field of semiconductor electronics and nanotechnology. The current level of sophistication in solid state technology and combinatorial materials science is very well capable of realizing our proposal and discover new superconductors.

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STM/STS study of superconducting diamond

Cited by 16 publications

References 24 publications

Spatially correlated microstructure and superconductivity in polycrystalline boron-doped diamond

Spatially correlated microstructure and superconductivity in polycrystalline boron-doped diamond

Superconducting and normal state properties of heavily hole-doped diamond synthesized at high pressure

Impurity band Mott insulators: a new route to highT_csuperconductivity

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STM/STS study of superconducting diamond

Cited by 16 publications

References 24 publications

Spatially correlated microstructure and superconductivity in polycrystalline boron-doped diamond

Spatially correlated microstructure and superconductivity in polycrystalline boron-doped diamond

Superconducting and normal state properties of heavily hole-doped diamond synthesized at high pressure

Impurity band Mott insulators: a new route to highTcsuperconductivity

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Impurity band Mott insulators: a new route to highT_csuperconductivity