Magic-Sized Diamond Nanocrystals

Altfeder, Igor; Hu, Jianjun; Voevodin, Andrey A.; Krim, J.

doi:10.1103/physrevlett.102.136104

Cited by 12 publications

(17 citation statements)

References 40 publications

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“…The ⌬ nanomodulation observed in sample s3 is in agreement with the rencent results reported by Altfeder et al, 13 who studied the surfaces of boron-doped diamond films by performing STM experiments. It has been found that these surfaces reveal spatially ordered magic-sized nanocrystals by showing an arrangement of the LDOS in parallelograms with base and height sizes equal to 8.3 and 10.5 nm, respectively.…”

Section: Intrinsic Granularitysupporting

confidence: 91%

“…It will be shown that our results are in agreement with the recent observation of modulated local density of states ͑LDOS͒ on surfaces of boron-doped diamond films. 13 On the other hand, the superconducting gap ⌬, extracted from the I-V curves measured at a fixed point and at different temperatures, shows its temperature dependence ͓⌬͑T͔͒ different from that predicted by the BCS theory. The ⌬͑T͒ is significantly affected between 2 and 1 K, below which it saturates.…”

Section: Introductionmentioning

confidence: 93%

“…It has been found that these surfaces reveal spatially ordered magic-sized nanocrystals by showing an arrangement of the LDOS in parallelograms with base and height sizes equal to 8.3 and 10.5 nm, respectively. 13 Such arrangement is completely absent in pure nondoped diamond samples and is claimed to be caused by the Fermi-sea-induced quantum electronic growth mechanism. 13 According to the latter, the electron de Broglie wavelength controls the geometry of the nanostructures, establishing a preferred size for them.…”

Section: Intrinsic Granularitymentioning

confidence: 99%

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Intrinsic granularity in nanocrystalline boron-doped diamond films measured by scanning tunneling microscopy

et al. 2009

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We report on low-temperature scanning tunneling microscopy/spectroscopy experiments performed on superconducting boron-doped nanocrystalline diamond ͑NCD͒ thin films prepared by chemical-vapor deposition methods. The most representative sample reveals the observed superconducting gap ͑⌬͒ highly modulated over a length scale on the order of ϳ30 nm, which is much shorter than the typical diamond grain size. The sample local and macroscopic behavior favors for the ⌬ modulation as being an intrinsic property of the NCD granules. On the other hand, ⌬ shows its temperature dependence ͓⌬͑T͔͒ consistent with the results obtained by Fominov and Feigel'man ͓Phys. Rev. B 63, 094518 ͑2001͔͒, who studied theoretically the behavior of the superconducting gap of a BCS superconductor in contact with a normal layer by solving the one-dimensional Usadel equations on the superconducting side of the superconducting to normal interface.

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Section: Intrinsic Granularitysupporting

confidence: 91%

Section: Introductionmentioning

confidence: 93%

Section: Intrinsic Granularitymentioning

confidence: 99%

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Intrinsic granularity in nanocrystalline boron-doped diamond films measured by scanning tunneling microscopy

et al. 2009

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“…Most of the junctions were found to be more transparent as can be seen following a line between positions 4 and 5 with progressive variations in the gray scale reminiscent of the superconducting proximity effect. We did not observe any quantum confinement effect 22 within a grain, presumably because of the strong intergrain coupling in our samples. Our results are in strong contrast with a recent STM study on one polycrystalline diamond film, where a strong and short-range modulation of the superconductivity was observed within the same grain.…”

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

confidence: 52%

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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“…On the other hand, diamond is an ideal candidate for electronic devices because of its extreme properties like high thermal conductivity, high mechanical strength, and optical transparency. 5,6 These extreme properties of diamond film have triggered many studies on diamond including its application in electronic devices under extreme operating conditions, where Si-, Ga-, and As-based devices are not suitable.…”

Section: Introductionmentioning

confidence: 99%

Free standing graphene-diamond hybrid films and their electron emission properties

Varshney

Rao

Guinel

et al. 2011

Journal of Applied Physics

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Free standing graphene-diamond hybrid films have been fabricated using saturated hydrocarbon polymers as seeding material by hot filament chemical vapor deposition technique. The films are characterized with x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron energy loss spectroscopy (EELS). The XRD shows the characteristic diffraction peaks of both diamond and graphene. The Raman spectrum shows the characteristic band of diamond at 1332 cm−1 and D, G, and 2D bands of graphene at 1349, 1592, and 2687 cm−1, respectively. Both SEM and TEM depict the presence of diamond and graphene in the films. The EELS recorded in the carbon K-edge region also shows the signature peaks of diamond and graphene. The free standing hybrid films exhibit a remarkably low turn-on field of about 2.4 V/μm and a high emission current density of 0.1 mA/cm2. Furthermore, emission currents are stable over the period of 7 days. The superior field emission characteristics of the free standing graphene-diamond hybrid films are attributed to the heat sink capability of diamond and high electrical conductivity of graphene.

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Magic-Sized Diamond Nanocrystals

Cited by 12 publications

References 40 publications

Intrinsic granularity in nanocrystalline boron-doped diamond films measured by scanning tunneling microscopy

Intrinsic granularity in nanocrystalline boron-doped diamond films measured by scanning tunneling microscopy

Spatially correlated microstructure and superconductivity in polycrystalline boron-doped diamond

Free standing graphene-diamond hybrid films and their electron emission properties

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