Low-temperature transport in highly boron-doped nanocrystalline diamond

Achatz, Philipp; Gajewski, Wojciech; Bustarret, Étienne; Marcenat, C.; Piquerel, Raoul; Chapelier, Claude; Dubouchet, Thomas; Williams, Oliver A.; Haenen, Ken; Garrido, José Antonio; Stutzmann, M.

doi:10.1103/physrevb.79.201203

Cited by 38 publications

(35 citation statements)

References 32 publications

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“…This behavior agrees with the observed significant width of the resistive transition, which is then related to the appearance of a percolating path through sufficiently well coupled superconducting grains with different gaps, as confirmed by susceptibility measurements. 13 The local ⌬͑0͒ / k B T c ratio values were found to be significantly lower than the 1.76 value expected for a conventional BCS superconductor. This could be explained by the inverse proximity effect due to the contact with grains with a weaker superconducting coupling.…”

Section: Fig 2 ͑Color Online͒ ͑A͒ Two-dimensional View Ofmentioning

confidence: 76%

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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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Section: Fig 2 ͑Color Online͒ ͑A͒ Two-dimensional View Ofmentioning

confidence: 76%

“…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.…”

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Spatially correlated microstructure and superconductivity in polycrystalline boron-doped diamond

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“…Soon after the theoretical prediction of equation (9), the electrical-transport properties of several granular systems were studied, including Pt/C composite nanowires [184,185], B-doped nano-crystalline diamond films [186], and granular Cr films [179]. The δσ ∝ ln T temperature law has been confirmed.…”

Section: Longitudinal Electrical Conductivitymentioning

confidence: 95%

Electronic conduction properties of indium tin oxide: single-particle and many-body transport

Lin

2014

J. Phys.: Condens. Matter

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Abstract.Indium tin oxide (Sn-doped In 2 O 3−δ or ITO) is an interesting and technologically important transparent conducting oxide. This class of material has been extensively investigated for decades, with research efforts focusing on the application aspects. The fundamental issues of the electronic conduction properties of ITO from 300 K down to low temperatures have rarely been addressed. Studies of the electricaltransport properties over a wide range of temperature are essential to unraveling the underlying electronic dynamics and microscopic electronic parameters. In this Topical Review, we show that one can learn rich physics in ITO material, including the semiclassical Boltzmann transport, the quantum-interference electron transport, and the electron-electron interaction effects in the presence of disorder and granularity. To reveal the avenues and opportunities that the ITO material provides for fundamental research, we demonstrate a variety of charge transport properties in different forms of ITO structures, including homogeneous polycrystalline films, homogeneous singlecrystalline nanowires, and inhomogeneous ultrathin films. We not only address new physics phenomena that arise in ITO but also illustrate the versatility of the stable ITO material forms for potential applications. We emphasize that, microscopically, the rich electronic conduction properties of ITO originate from the inherited freeelectron-like energy bandstructure and low-carrier concentration (as compared with that in typical metals) characteristics of this class of material. Furthermore, a low carrier concentration leads to slow electron-phonon relaxation, which causes (i) a small residual resistance ratio, (ii) a linear electron diffusion thermoelectric power in a wide temperature range 1-300 K, and (iii) a weak electron dephasing rate. We focus our discussion on the metallic-like ITO material.

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“…There is some evidence to suggest that boron is incorporated more efficiently in some growth directions than others [28], and that an adjustment of the methane concentration in BNCD growth can affect the overall dopant concentration leading to the reporting of some contradictory results [24,25]. Given the tunability of CVD diamond growth, it is no surprise that there is a wide variation in the properties of polycrystalline superconducting diamond reported in the literature [10,24,25,27,[29][30][31][32]. It is exactly this tunability, however, that is a powerful tool in the well-controlled production of this granular superconducting material.…”

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Fluctuation spectroscopy as a probe of granular superconducting diamond films

Klemencic

Fellows

Werrell

et al. 2017

Phys. Rev. Materials

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We present resistance versus temperature data for a series of boron-doped nanocrystalline diamond films whose grain size is varied by changing the film thickness. Upon extracting the fluctuation conductivity near to the critical temperature we observe three distinct scaling regions -3D intragrain, quasi-0D, and 3D intergrain -in confirmation of the prediction of Lerner, Varlamov and Vinokur. The location of the dimensional crossovers between these scaling regions allows us to determine the tunnelling energy and the Thouless energy for each film. This is a demonstration of the use of fluctuation spectroscopy to determine the properties of a superconducting granular system. Tunable granular materials offer rich physical systems with which to study the interplay between electron correlations and the mesoscopic effects of disorder. The occurrence of the metal-insulator and superconductorinsulator transitions appear to be strongly linked to granularity, be it structural or pertaining to variations of the order parameter [1][2][3]. There are also clear theoretical predictions for the signature of granularity in the transport properties of disordered superconductors close to the superconducting transition [4][5][6][7]. Boron doped nanocrystalline diamond (BNCD) provides a suitable tuneable material in which to explore these theoretical predictions. Superconductivity was first observed in high-pressure, high-temperature fabricated boron doped diamond in 2004 [8]. The phenomenon was quickly demonstrated in both single-crystalline [9] and polycrystalline [10] diamond synthesised by chemical vapour deposition (CVD). While superconductivity in doped semiconductor materials [11,12] is an active area of research, and although nanocrystalline diamond retains many of the desirable mechanical properties of single-crystalline material [13], a sometimes overlooked property in the study of superconductivity in polycrystalline boron-doped diamond is the physical granularity itself.A clear experimental signature of superconducting granular systems, as pointed out by Lerner, Varlamov and Vinokur [5] (henceforth referred to as LVV), is that there are three distinct temperature regimes in the vicinity of the critical temperature (T c ), distinguished by the magnitude of the temperature-dependent GinzburgLandau coherence length. At temperatures immediately above T c , short-lived Cooper pairs act as charge carriers, modifying the conductivity. The principal modification close to T c is the Aslamazov-Larkin pair contribution to the conductivity -the so-called paraconductivity [14]. When the coherence length is much larger than the typical grain size, the granularity is not seen by a Cooper pair and the system behaves as a 3D superconductor with paraconductivity taking the well-known form ∝ −1/2 , where = (T − T c )/T c is the reduced temperature. When the coherence length is comparable to the typical grain size, each grain acts as its own 0D superconductor for which the paraconductivity is expected to be ∝ −2 . However, in addition, the...

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Low-temperature transport in highly boron-doped nanocrystalline diamond

Cited by 38 publications

References 32 publications

Spatially correlated microstructure and superconductivity in polycrystalline boron-doped diamond

Spatially correlated microstructure and superconductivity in polycrystalline boron-doped diamond

Electronic conduction properties of indium tin oxide: single-particle and many-body transport

Fluctuation spectroscopy as a probe of granular superconducting diamond films

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