Dopant-site effect in superconducting diamond (111) studied by atomic stereophotography

Kato, Y.; Matsui, Fumihiko; Shimizu, Tatsuya; Daimon, Hiroshi; Matsushita, Teruo; Guo, Fang; Tsuno, Takashi

doi:10.1063/1.2824844

Cited by 33 publications

(21 citation statements)

References 18 publications

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Section: ) Superconducting Semiconductors : From Early Predictions Tmentioning

confidence: 99%

“…Then, bridging the gap separating the super-hardness and superconductivity communities, doped diamond was found to be superconducting around 4K [3] , paving the way for systematic studies of superhard superconducting materials [29] . Since then, superconducting polycrystalline, single crystal or even nanocrystalline boron-doped diamond samples have been synthesized by a large number of groups using the original HPHT [30] techniques or alternative chemical vapor deposition growth techniques [31][32][33][34][35] , and transition temperatures up to 10 K have been reported [36] .In 2006, using a gas immersion laser doping (GILD) technique (see box 3), which allows to dope silicon well beyond the thermodynamic solubility limit, a superconducting transition in highly boron-doped silicon was reported with a T C around 0.35 K for a boron concentration of the order of 8 at.% [4,37] . Finally, a superconducting transition was also observed recently in boron-doped SiC [5,6] with a T C of 1.4 K. In all three cases (diamond, Si and SiC), boron was the source of hole-doping.…”

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confidence: 99%

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Superconducting group-IV semiconductors

et al. 2009

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We present recent achievements and predictions in the field of doping-induced superconductivity in column IV-based covalent semiconductors, with a focus on Bdoped diamond and silicon. Despite the amount of experimental and theoretical work produced over the last four years, many open questions and puzzling results remain to be clarified. The nature of the coupling (electronic correlation and/or phonon-mediated), the relationship between the doping concentration and the critical temperature (T C ), which determines the prospects for higher transition temperatures, as well as the influence of disorder and dopant homogeneity, are debated issues that will determine the future of the field. We suggest that innovative superconducting devices, combining specific properties of diamond or silicon, and the maturity of semiconductor-based technologies, will soon be developed. 1) IntroductionIt was probably the discovery of a superconducting transition around 40 K in the rather simple MgB 2 compound [1] that revived the interest for a specific class of superconducting materials, belonging to the so-called covalent metals [2] . These superconducting covalent systems (see box 1), including B-doped diamond [3] , silicon [4] , and silicon carbide [5,6] , Ba-doped silicon clathrates [7,8] , alkali-doped fullerenes [9,10] and the CaC 6 or YbC 6 intercalated graphites [11,12] , share the specificity of involving at least one relatively light element and of preserving strongly directional covalent bonds in their metallic state. The implications of this covalent character are important in superconductors in which Cooper pairs are coupled through phonons. The use of perturbation theory to study the renormalisation of the electron-electron repulsion by the electron-phonon interaction leads to the so-called Eliashberg equations [13] and to the celebrated McMillan formula [13] relating, in an approximate way, the superconducting transition temperature T C to an average phonon frequency ω ln , the electron-phonon coupling parameter λ ep and the screened and retarded Coulomb repulsion parameter µ*: Clearly, low atomic masses lead to high frequency phonon modes, which may enhance the ω ln prefactor and thus T C . This is the basis of the so-called isotope effect. Furthermore, strong covalent bonding will lead both to large phonon frequencies and a large electron-phonon coupling potential V ep =λ ep /N(E F ), with N(E F ) the density of states at the Fermi level, also contributing to enhance T C . Even within a phonon-mediated coupling scenario, these criteria do not necessarily warrant a large T C since increasing λ ep may also lead to a lattice instability, and a large electron-phonon potential V ep may be impaired by a low density N(E F ). However, these simple considerations, as well as more elaborate surveys and predictions of a larger T C [14][15][16] , have provided much incentive to study this class of materials.The most familiar covalent systems are certainly diamond and silicon. The former can be considered as the prototype insula...

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Section: ) Superconducting Semiconductors : From Early Predictions Tmentioning

confidence: 99%

mentioning

confidence: 99%

Superconducting group-IV semiconductors

et al. 2009

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“…For instance, crystal orientation during doping processes have been reported to play a crucial role [11]. Since nonequilibrium preparations almost inevitably introduce disorder down to the atomic scale, its impact on superconductivity -which up to now remains uncertain -must be considered.…”

Section: Introductionmentioning

confidence: 99%

The impact of heavy Ga doping on superconductivity in germanium

Skrotzki

Herrmannsdörfer

Heera

et al. 2011

Low Temperature Physics

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We report new experimental results on how superconductivity in gallium-doped germanium (Ge:Ga) is influenced by hole concentration and microstructure. Ion implantation and subsequent flash-lamp annealing at various temperatures have been utilized to prepare highly p-doped thin films consisting of nanocrystalline and epitaxially grown sublayers with Ga-peak concentrations of up to 8 at.%. Successive structural investigations were carried out by means of Rutherford-backscattering spectrometry in combination with ion channelling, secondaryion-mass spectrometry, and high-resolution cross-sectional transmission electron microscopy. Hole densities of 1.8·10 20 to 5.3·10 20 cm -3 (0.4 to 1.2 at.%) were estimated via Hall-effect measurements revealing that only a fraction of the incorporated gallium has been activated electrically to generate free charge carriers. The coincidence of a sufficiently high hole and Ga concentration is required for the formation of a superconducting condensate. Our data reflect a critical hole concentration of around 0.4 at.%. Higher concentrations lead to an increase of T c from 0.24 to 0.43 K as characterized by electrical-transport measurements. A short mean-free path indicates superconductivity in the dirty limit. In addition, small critical-current densities of max. 20 kA/m 2 point to a large impact of the microstructure.PACS: 74.10.+v Occurrence, potential candidates; 74.78.-w Superconducting films and low-dimensional structures.

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“…PIAD from the sample at specific kinetic energy is most efficiently measured by a two-dimensional display-type spherical mirror analyzer (DIANA) [16][17][18] which enables measurement of a two-dimensional angular distribution snapshot of specific kinetic energy electron [10][11][12][19][20][21][22]. Figure 1 is a schematic diagram of DIANA and measurement set up.…”

Section: Methodsmentioning

confidence: 99%

“…FFP rotational shift caused by circularly polarized light excitation was shown to be inversely proportional to the distance between the emitter and scatterer atoms both experimentally [8] and theoretically [9]. Taking advantage of this circular dichroism, a stereo atomscope was realized [10][11][12]. Even a real time visualization has been achieved [13].…”

Section: Introductionmentioning

confidence: 99%