Boron concentration dependence of Raman spectra on {100} and {111} facets of B-doped CVD diamond

Ushizawa, Koichi; Watanabe, Kenji; Ando, Toshihiro; Sakaguchi, Isao; Nishitani‐Gamo, Mikka; Sato, Yoichiro; Kanda, H.

doi:10.1016/s0925-9635(98)00296-9

Cited by 190 publications

(144 citation statements)

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“…Upon cooling from the high temperature synthesis conditions, some diamond grains may react more efficiently with boron to form an intergrowth structure having different B concentrations. There are two additional factors, possibly related to the first, that contribute to inhomogeneity of B-doped diamond, irrespective of the preparation technique: (a) B atoms substitute for C at low doping levels; whereas, at high doping levels, additional boron atoms enter the diamond structure interstitially and strain the lattice [22]; and (b) boron atoms are incorporated preferentially in certain growth sectors [23,24]. In the absence of specific knowledge of the growth morphology and B distribution in our samples, it is not possible to make definitive statements about the origin of inhomogeneity; although, preferential B uptake in certain growth sectors provides a plausible mechanism to account for the specific heat behaviors of the present sample.…”

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Superconducting and normal-state properties of heavily hole-doped diamond

et al. 2005

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We report measurements of the specific heat, Hall effect, upper critical field and resistivity on bulk, B-doped diamond prepared by reacting amorphous B and graphite under high-pressure/high-temperature conditions. These experiments establish unambiguous evidence for bulk superconductivity 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.PACS numbers: 74.10.+v, 74.62.Bf, The theoretical prediction [1] and nearly simultaneous discovery of superconductivity in self-doped degenerate semiconductors, such as Ge x Te [2], Sn x Te [3] and SrTiO 3-δ [4], was, at the time, an important validation of the recently developed BCS theory of superconductivity and of current understanding of electron-electron and electron-phonon interactions. The basic premise of these predictions was that superconductivity would be favored in doped semiconductors with many-valley band structures due to their relatively enhanced density of electronic states and the attractive interaction provided by intervalley phonon scattering. As expected, the superconducting transition temperatures of these systems were relatively low, with T c s < 0.5 K. Diamond-structured Si and Ge, which have mutli-valley band structures [5], likewise were predicted to have T c s near 0.005 K when carrier doped at a concentration ≈10 20 cm -3 [1], but superconductivity has not been found in their diamond structure. Recently, however, superconductivity was reported in diamond itself when hole-doped by B additions.[6] Because of its small atomic radius, B is incorporated relatively easily into the dense diamond lattice and, with one less electron than C, dopes holes into a shallow acceptor level close to the top of the valence band. Assuming that each of the approximately ≈ 4.9x10 21 B/cm 3 in this superconductor contributed 1 hole/B to diamond, this hole density exceeded n IM ∼2x10 20 cm -3 that is necessary to induce an insulator-metal transition; beyond this carrier concentration, the impurity band formed by donor states begins to overlap the valence band edge. [7] The superconducting transition temperature, T c ≈ 4K, of hole-doped diamond is substantially higher than predicted for diamond-structured Si or Ge, even if they were doped hypothetically to n ∼10 21 cm -3 .[8]Besides the existence of superconductivity, relatively little else is known to constrain interpretations of the superconducting mechanism in diamond. On the basis of existing information, two qualitatively different views have emerged: superconductivity is electron-phonon mediated [9][10][11][12] or arises from a resonating valence bond type of mechanism [13]. Though differing in detail, models of a conventional mechanism conclude that holes doped into the degenerate σ-bonding valence band are coupled most strongly by zone-center optical phonon modes that soften as holes are added. This mechanism is analogous to that producing superconductivity near 40 K in MgB 2 , [1...

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Superconducting and normal-state properties of heavily hole-doped diamond

et al. 2005

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“…49 Such phonon-related interactions cause the asymmetry and broadening of the diamond peak at the Raman spectrum. 50 Therefore, the diamond peak is barely visible especially for the NCD1 and NCD0.2 films. Note that the B-doping level close to the nucleation surface of the diamond film (NCD1-nucl) is expected to be slightly lower compared to the growth surface (NCD1).…”

Section: Methodsmentioning

confidence: 98%

Effect of Boron Doping on the Wear Behavior of the Growth and Nucleation Surfaces of Micro- and Nanocrystalline Diamond Films

Buijnsters

Tsigkourakos

Hantschel

et al. 2016

ACS Appl. Mater. Interfaces

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Effect of boron doping on the wear behavior of the growth and nucleation surfaces of micro-and nanocrystalline diamond films Buijnsters CopyrightOther than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons. Takedown policyPlease contact us and provide details if you believe this document breaches copyrights. We will remove access to the work immediately and investigate your claim. ABSTRACT: B-doped diamond has become the ultimate material for applications in the field of microelectromechanical systems (MEMS), which require both highly wear resistant and electrically conductive diamond films and microstructures. Despite the extensive research of the tribological properties of undoped diamond, to date there is very limited knowledge of the wear properties of highly B-doped diamond. Therefore, in this work a comprehensive investigation of the wear behavior of highly B-doped diamond is presented. Reciprocating sliding tests are performed on micro-and nanocrystalline diamond (MCD, NCD) films with varying B-doping levels and thicknesses. We demonstrate a linear dependency of the wear rate of the different diamond films with the B-doping level. Specifically, the wear rate increases by a factor of 3 between NCD films with 0.6 and 2.8 at. % B-doping levels. This increase in the wear rate can be linked to a 50% decrease in both hardness and elastic modulus of the highly B-doped NCD films, as determined by nanoindentation measurements. Moreover, we show that fine-grained diamond films are more prone to wear. Particularly, NCD films with a 3× smaller grain size but similar B-doping levels exhibit a double wear rate, indicating the crucial role of the grain size on the diamond film wear behavior. On the other hand, MCD films are the most wear-resistant films due to their larger grains and lower B-doping levels. We propose a graphical scheme of the wear behavior which involves planarization and mechanochemically driven amorphization of the surface to describe the wear mechanism of B-doped diamond films. Finally, the wear behavior of the nucleation surface of NCD films is investigated for the first time. In particular, the nucleation surface is shown to be susceptible to higher wear compared to the growth surface due to its higher grain boundary line density.

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“…23,24 Finally, the influence of the boron acceptor on the structural and optoelectronic properties of the diamond films were investigated for single and polycrystalline diamond films. 21,22,[26][27][28][29][30][31] However, the same sort of detailed investigation is still missing for boron-doped NCD films. As it has been discussed for polycrystalline diamond films 22 and UNCD films, 32 it is essential to understand the influence of the grain boundaries on the optical properties of NCD and the role they play in the electronic transport.…”

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confidence: 99%

Electronic and optical properties of boron-doped nanocrystalline diamond films

et al. 2009

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We report on the electronic and optical properties of boron-doped nanocrystalline diamond (NCD) thin films grown on quartz substrates by CH 4 /H 2 plasma chemical vapor deposition.Diamond thin films with a thickness below 350 nm and with boron concentration ranging from 10 17 cm -3 to 10 21 cm -3 have been investigated. UV Raman spectroscopy and AFM have been used to assess the quality and morphology of the diamond films. Hall effect measurements confirmed the expected p-type conductivity. At room temperature, the conductivity varies from 1.5x10 -8 Ω -1 cm -1 for a non-intentionally doped film up to 76 Ω -1 cm -1 for a heavily B-doped film. Increasing the doping level results in a higher carrier concentration while the mobility decreases from 1.8 cm 2 V -1 s -1 down to 0.2 cm 2 V -1 s -1 . For NCD films with low boron concentration, the conductivity strongly depends on temperature. However, the conductivity and the carrier concentration are no longer temperature-dependent for films with the highest boron doping, and the NCD films exhibit metallic properties. Highly doped films show superconducting properties with critical temperatures up to 2K. The critical boron concentration for the metal-insulator transition is in the range from 2x10 20 cm -3 up to 3x10 20 cm -3 . We discuss different transport mechanisms to explain the influence of the grain boundaries and boron doping on the electronic properties of NCD films. Valence band transport dominates at low boron concentration and high temperatures, 2 whereas hopping between boron acceptors is the dominant transport mechanism for boron doping concentration close to the Mott transition. Grain boundaries strongly reduce the mobility for low and very high doping levels. However, at intermediate doping levels where hopping transport is important, grain boundaries have a less pronounced effect on the mobility. The influence of boron and the effect of grain boundaries on the optoelectronic properties of the NCD films are examined using spectrally resolved photocurrent measurements and photothermal deflection spectroscopy. Major differences occur in the low energy range, between 0.5 -1.0 eV, where both Boron impurities and the sp 2 carbon phase in the grain boundaries govern the optical absorption.

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Boron concentration dependence of Raman spectra on {100} and {111} facets of B-doped CVD diamond

Cited by 190 publications

References 14 publications

Superconducting and normal-state properties of heavily hole-doped diamond

Superconducting and normal-state properties of heavily hole-doped diamond

Effect of Boron Doping on the Wear Behavior of the Growth and Nucleation Surfaces of Micro- and Nanocrystalline Diamond Films

Electronic and optical properties of boron-doped nanocrystalline diamond films

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