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M.C. Polo

Bio: M.C. Polo is an academic researcher from University of Barcelona. The author has contributed to research in topics: Thin film & Diamond. The author has an hindex of 20, co-authored 55 publications receiving 1217 citations.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the influence of negative bias voltage applied to substrates and the nitrogen background pressure (up to 10−3 Torr) on film properties was studied by scanning electron microscopy (SEM) and electron energy loss spectroscopy (EELS).

154 citations

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TL;DR: The relationship between metal-induced (W, Mo, Nb and Ti) structures and the surface properties of Me-DLC thin films is discussed in this article, which shows the possibilities of controlling the amorphous carbon films structure and surface properties by introducing metal in the DLC matrix.

81 citations

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TL;DR: In this paper, the preparation of metal containing hydrogenated amorphous carbon (a-C:H) thin films by means of reactive magnetron sputtering with pulsed d.c.f. bias using different gas mixtures of methane and argon was discussed.
Abstract: We discuss the preparation of metal containing hydrogenated amorphous carbon (a-C:H) thin films by means of reactive magnetron sputtering with pulsed d.c. power of a metal target (W, Mo, Nb, Ti) and r.f. bias using different gas mixtures of methane and argon. The obtained samples comprised a thickness between 100 and 600 nm and a low internal stress when little quantities of metal were incorporated. The chemical composition was analysed by X-ray Photoelectron Spectroscopy (XPS). Depth profile composition was qualitatively displayed by secondary ion mass spectrometry (SIMS). The optical characterization of the films was carried out by transmittance measurements in the visible range and showed a relationship between the optical band gap and the composition. Structural information was obtained by X-ray diffraction (XRD), whose results showed a shift of the Bragg peaks from carbide crystallites as the metal amount increased. Peak width calculations situated particle sizes in the nanometric range. Surface topography from atomic force microscopy (AFM) measurements is also discussed. Surface energy was measured by the contact angle technique. The internal stress of the films was obtained by profilometry and a relationship with their structure was found. The results are compared with those corresponding to metal-free (pure) a-C:H films.

73 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of the different metal induced structures on the electrical, optical and mechanical properties of diamond-like carbon (DLC) thin films were studied, where samples were prepared at room temperature by pulsed-DC reactive magnetron sputtering, as a suitable way to vary their composition.

68 citations

Journal ArticleDOI
TL;DR: In this article, the internal stress and strain in boron-doped diamond films grown by microwave plasma chemical vapor deposition (MWCVD) and hot filament CVD (HFCVD) were studied as a function of borone concentration.
Abstract: The internal stress and strain in boron‐doped diamond films grown by microwave plasma chemical vapor deposition (MWCVD) and hot filament CVD (HFCVD) were studied as a function of boron concentration. The total stress (thermal+intrinsic) was tensile, and the stress and strain increased with boron concentration. The stress and the strain measured in HFCVD samples were greater than those of MWCVD samples at the same boron concentration. The intrinsic tensile stress, 0.84 GPa, calculated by the grain boundary relaxation model, was in good agreement with the experimental value when the boron concentration in the films was below 0.3 at.%. At boron concentrations above 0.3 at.%, the tensile stress was mainly caused by high defect density, and induced by a node‐blocked sliding effect at the grain boundary.

61 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the structures of various types of amorphous carbon films and common characterization techniques are described, which can be classified as polymer-like, diamond-like or graphite-like based on the main binding framework.

1,004 citations

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TL;DR: In this article, the authors present a survey on the recent progress in laser ablation of a solid target in a confining liquid for the synthesis of nanocrystals with focus on the mechanism of the nanocrystal growth.

898 citations

Journal ArticleDOI
TL;DR: Experimental and theoretical results indicate that the bonded case cannot, while the separated one can, turn the inert CNTs into ORR electrocatalysts, demonstrating the crucial role of the doping microstructure on ORR performance.
Abstract: Two kinds of boron and nitrogen co-doped carbon nanotubes (CNTs) dominated by bonded or separated B and N are intentionally prepared, which present distinct oxygen reduction reaction (ORR) performances. The experimental and theoretical results indicate that the bonded case cannot, while the separated one can, turn the inert CNTs into ORR electrocatalysts. This progress demonstrates the crucial role of the doping microstructure on ORR performance, which is of significance in exploring the advanced C-based metal-free electrocatalysts.

816 citations

Journal ArticleDOI
TL;DR: In this paper, a general framework for the interpretation of infrared and Raman spectra of amorphous carbon nitrides is presented, which can be used to explain the large dynamic charge of the more delocalized bonding which occurs in more than two bonded networks.
Abstract: A general framework for the interpretation of infrared and Raman spectra of amorphous carbon nitrides is presented. In the first part of this paper we examine the infrared spectra. The peaks around 1350 and 1550 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ found in the infrared spectrum of amorphous carbon nitride or hydrogenated and hydrogen-free amorphous carbon are shown to originate from the large dynamic charge of the more delocalized \ensuremath{\pi} bonding which occurs in more ${\mathrm{sp}}^{2}$ bonded networks. The IR absorption decreases strongly when the \ensuremath{\pi} bonding becomes localized, as in tetrahedral amorphous carbon. Isotopic substitution is used to assign the modes to $\mathrm{C}=\mathrm{C}$ skeleton modes, even those modes around 1600 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ which become strongly enhanced by the presence of hydrogen. The infrared spectrum of carbon nitride may resemble the Raman spectrum at some excitation energy, but the infrared activity does not primarily result from nitrogen breaking the symmetry. In the second part we examine the Raman spectra. A general model is presented for the interpretation of the Raman spectra of amorphous carbon nitrides measured at any excitation energy. The Raman spectra can be explained in terms of an amorphous carbon based model, without need of extra peaks due to CN, NN, or NH modes. We classify amorphous carbon nitride films in four classes, according to the corresponding N-free film: $a\ensuremath{-}\mathrm{C}:\mathrm{N},$ $a\ensuremath{-}\mathrm{C}:\mathrm{H}:\mathrm{N},$ $ta\ensuremath{-}\mathrm{C}:\mathrm{H}:\mathrm{N},$ and $ta\ensuremath{-}\mathrm{C}:\mathrm{N}.$ We analyze a wide variety of samples for the four classes and present the Raman spectra as a function of N content, ${\mathrm{sp}}^{3}$ content, and band gap. In all cases, a multiwavelength Raman study allows a direct correlation of the Raman parameters with the N content, which is not generally possible for single wavelength excitation. The G peak dispersion emerges as a most informative parameter for Raman analysis. UV Raman enhances the ${\mathrm{sp}}^{1}$ CN peak, which is usually too faint to be seen in visible excitation. As for N-free samples, UV Raman also enhances the C-C ${\mathrm{sp}}^{3}$ bonds vibrations, allowing the ${\mathrm{sp}}^{3}$ content to be quantified.

674 citations

Journal ArticleDOI
TL;DR: In this paper, the authors examined the stress associated with crystallite coalescence during the initial stages of growth in thin polycrystalline films with island growth morphology and predicted large tensile stresses in agreement with experimental results.
Abstract: We examined the stress associated with crystallite coalescence during the initial stages of growth in thin polycrystalline films with island growth morphology. As growing crystallites contacted each other at their bases, the side-walls zipped together until a balance was reached between the energy associated with eliminating surface area, creating a grain boundary and straining the film. Our estimate for the resulting strain depends only on interfacial free energies, elastic properties, and grain size and predicts large tensile stresses in agreement with experimental results. We also discuss possible stress relaxation mechanisms that can occur during film growth subsequent to the coalescence event.

554 citations